U.S. patent application number 14/008523 was filed with the patent office on 2014-01-16 for ink jet ink, ink cartridge, and ink jet recording method.
This patent application is currently assigned to CANON KABUSHIKI KAISHA. The applicant listed for this patent is Hiromitsu Kishi, Kenji Moribe, Daiji Okamura, Kouichirou Okumura, Kenichi Shiiba, Kousuke Yamasaki. Invention is credited to Hiromitsu Kishi, Kenji Moribe, Daiji Okamura, Kouichirou Okumura, Kenichi Shiiba, Kousuke Yamasaki.
Application Number | 20140015895 14/008523 |
Document ID | / |
Family ID | 46930095 |
Filed Date | 2014-01-16 |
United States Patent
Application |
20140015895 |
Kind Code |
A1 |
Okamura; Daiji ; et
al. |
January 16, 2014 |
INK JET INK, INK CARTRIDGE, AND INK JET RECORDING METHOD
Abstract
To provide an ink jet ink that produces an image having high
optical density, scratch resistance, and highlighter resistance,
has excellent ink ejection stability, and can reduce image
deflection caused by face wetting. The ink jet ink contains a
polyurethane polymer and a self-dispersing pigment. The
polyurethane polymer has units derived from a polyisocyanate, a
polyol having no acid group, and a diol having an acid group. The
molar ratio of the percentage of the urethane bond in the
polyurethane polymer to the percentage of the urea bond in the
polyurethane polymer is 85.0/15.0 or more and 100.0/0 or less.
Inventors: |
Okamura; Daiji; (Tokyo,
JP) ; Yamasaki; Kousuke; (Kawasaki-shi, JP) ;
Moribe; Kenji; (Fujisawa-shi, JP) ; Okumura;
Kouichirou; (Kawasaki-shi, JP) ; Shiiba; Kenichi;
(Warabi-shi, JP) ; Kishi; Hiromitsu;
(Kawasaki-shi, JP) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Okamura; Daiji
Yamasaki; Kousuke
Moribe; Kenji
Okumura; Kouichirou
Shiiba; Kenichi
Kishi; Hiromitsu |
Tokyo
Kawasaki-shi
Fujisawa-shi
Kawasaki-shi
Warabi-shi
Kawasaki-shi |
|
JP
JP
JP
JP
JP
JP |
|
|
Assignee: |
CANON KABUSHIKI KAISHA
Tokyo
JP
|
Family ID: |
46930095 |
Appl. No.: |
14/008523 |
Filed: |
March 19, 2012 |
PCT Filed: |
March 19, 2012 |
PCT NO: |
PCT/JP2012/001891 |
371 Date: |
September 27, 2013 |
Current U.S.
Class: |
347/21 ; 347/100;
347/86; 524/381; 524/396; 524/423; 524/590 |
Current CPC
Class: |
C09D 11/322 20130101;
C09D 11/102 20130101; C09D 11/54 20130101; C09D 175/04 20130101;
B41J 2/01 20130101; B41J 2/17503 20130101; C09D 11/30 20130101 |
Class at
Publication: |
347/21 ; 347/86;
347/100; 524/590; 524/396; 524/423; 524/381 |
International
Class: |
C09D 11/00 20060101
C09D011/00; B41J 2/01 20060101 B41J002/01; B41J 2/175 20060101
B41J002/175 |
Foreign Application Data
Date |
Code |
Application Number |
Mar 30, 2011 |
JP |
2011-075884 |
Mar 30, 2011 |
JP |
2011-075885 |
Claims
1. An ink jet ink, comprising: a polyurethane polymer and a
self-dispersing pigment, the polyurethane polymer having units
derived from a polyisocyanate, a polyol having no acid group, and a
diol having an acid group, wherein the polyol having no acid group
contains a polyether polyol having no acid group, and the
percentage (% by mole) constituted by a unit derived from the
polyether polyol having no acid group with respect to all the units
derived from the polyol having no acid group is 80% by mole or
more, the polyether polyol has a number-average molecular weight of
450 or more and 4,000 or less, the ratio of the percentage (% by
mole) of urethane bonds in the polyurethane polymer to the
percentage (% by mole) of urea bonds in the polyurethane polymer is
85.0/15.0 or more and 100.0/0 or less, and the diol having an acid
group is at least one selected from dimethylolpropionic acid and
dimethylolbutanoic acid, and the acid value of the polyurethane
polymer resulting from the unit(s) derived from the diol having an
acid group is 40 mgKOH/g or more and 140 mgKOH/g or less.
2. The ink jet ink according to claim 1, wherein the polyisocyanate
contains a hexamethylene diisocyanate, and the percentage (% by
mole) constituted by the unit(s) derived from the hexamethylene
diisocyanate with respect to all the units derived from the
polyisocyanate in the polyurethane polymer is 10% by mole or more
and 90% by mole or less.
3. The ink jet ink according to claim 1, wherein the polyurethane
polymer is a cross-linked polyurethane polymer.
4. The ink jet ink according to claim 1, wherein the ratio of the
percentage (% by mole) of urethane bonds in the polyurethane
polymer to the percentage (% by mole) of urea bonds in the
polyurethane polymer is 85.0/15.0 or more and 98.5/1.5 or less.
5. The ink jet ink according to claim 1, wherein the polyether
polyol having no acid group contains at least one selected from
poly(ethylene glycol), poly(propylene glycol), poly(1,2-butylene
glycol), and poly(1,3-butylene glycol).
6. The ink jet ink according to claim 1, wherein the polyether
polyol having no acid group contains poly(propylene glycol).
7. The ink jet ink according to claim 1, wherein the ratio of the
polyurethane polymer content (% by mass) of the ink to the
self-dispersing pigment content (% by mass) based on the total mass
of the ink is 0.05 or more and 2.00 or less.
8. The ink jet ink according to claim 1, further comprising a
salt.
9. The ink jet ink according to claim 8, wherein the salt contains
at least one anion selected from Cl.sup.-, Br.sup.-, I.sup.-,
ClO.sup.-, ClO.sup.2-, ClO.sup.3-, ClO.sup.4-, NO.sup.2-,
NO.sup.3-, SO.sub.4.sup.2-, CO.sub.3.sup.2-, HCOO.sup.-,
CH.sub.3COO.sup.-, C.sub.2H.sub.4(COO.sup.-).sub.2,
C.sub.6H.sub.5COO.sup.-, and C.sub.6H.sub.4(COO.sup.-).sub.2.
10. An ink cartridge, comprising an ink storage portion configured
to store an ink, wherein the ink is an ink jet ink according to
claim 1.
11. An ink jet recording method, comprising ejecting an ink by an
ink jet method, wherein the ink is an ink jet ink according to
claim 1.
12. An ink jet recording method, comprising: ejecting an ink
containing a pigment and a polyurethane polymer through an ink jet
recording head onto a recording medium; and applying a liquid
composition to the recording medium such that the liquid
composition at least partly overlaps the ink, the liquid
composition destabilizing the dispersion of the pigment in the ink
and decreasing the solubility of the polyurethane polymer, wherein
the ink is an ink jet ink according to claim 1.
Description
TECHNICAL FIELD
[0001] The present invention relates to an ink jet ink, an ink
cartridge containing the ink jet ink, and an ink jet recording
method.
BACKGROUND ART
[0002] In recent years, various important characteristics have been
required for ink jet inks, for example, ink reliability (including
ejection stability and ejection accuracy), image quality (including
high optical density), and image fastness (including scratch
resistance and highlighter resistance). In order to improve these
characteristics, various pigment inks containing a polyurethane
polymer have been studied (PTLs 1 to 4). PTL 1 discloses an aqueous
ink jet ink that contains a dispersion of a polyurethane polymer
having an acid group and a self-dispersing pigment. PTL 2 discloses
a pigment dispersion that contains a polyurethane polymer, which
contains a compound having three or more hydroxy groups and a soft
segment having a carboxy group. The soft segment contains a polyol.
PTL 3 discloses an aqueous pigment ink containing a polyurethane
polymer in which the ratio of the urethane bond to the urea bond is
specified. PTL 4 discloses an aqueous pigment ink that contains a
polyurethane polymer having no urea bond.
CITATION LIST
Patent Literature
[0003] PTL 1: PCT Japanese Translation Patent Publication No.
2005-515289 [0004] PTL 2: Japanese Patent Laid-Open No. 2008-179657
[0005] PTL 3: Japanese Patent Laid-Open No. 9-291242 [0006] PTL 4:
Japanese Patent Laid-Open No. 2004-285344
SUMMARY OF INVENTION
Technical Problem
[0007] The present inventors found that conventional pigment inks
containing a polyurethane polymer have improved ink reliability,
image quality, and image fastness but still do not sufficiently
satisfy the requirements.
[0008] The present inventors found that use of the polyurethane
polymer described in PTL 1 results in an acid value as low as
approximately 20 to 30 mgKOH/g and consequently poor ink ejection
stability. It was also found that a polyurethane polymer that
contains 10% by mole or more of a compound having three or more
hydroxy groups based on all the compounds having a hydroxy group as
disclosed in PTL 2 becomes excessively rigid, resulting in poor
image fastness. It was also found that the polyurethane polymer
disclosed in PTL 2 has an acid value as low as 30 mgKOH/g,
resulting in poor ink ejection stability.
[0009] In the polyurethane polymer disclosed in PTL 3, the molar
ratio of the urethane bond to the urea bond is in the range of
80/20 to 50/50. The present inventors found that the ejection of
such an ink containing a polyurethane polymer as disclosed in PTL 3
through an ink jet recording head results in the deposition of a
polymer component of the ink on a surface of the recording head on
which the ejection ports are disposed (hereinafter referred to as a
"face"). This phenomenon is referred to as "face wetting". The
polymer component deposited on the face may change the intended
flight direction of an ejected ink droplet. This deflection may be
small immediately after the ejection of the ink droplet but
increase before reaching a recording medium, causing a problem of
the deflection of some dots in the image (hereinafter referred to
as "image deflection"). This image deflection occurs not only in a
thermal ink jet method but also in an ink jet method involving the
use of a piezoelectric element.
[0010] The polyurethane polymer disclosed in PTL 4 has no urea
bond. Thus, the aqueous pigment ink disclosed in PTL 4 rarely
causes image deflection. However, because of the use of a
polymer-dispersed pigment, a desired optical density cannot be
achieved.
[0011] Accordingly, the present invention provides an ink jet ink
that produces an image having high optical density, scratch
resistance, and highlighter resistance, has excellent ink ejection
stability, and can reduce image deflection caused by face wetting.
The present invention also provides an ink cartridge containing an
ink according to an embodiment of the present invention and an ink
jet recording method.
Solution to Problem
[0012] These objects can be achieved by the present invention
described below. An ink jet ink according to one aspect of the
present invention contains a polyurethane polymer and a
self-dispersing pigment. The polyurethane polymer has units derived
from a polyisocyanate, a polyol having no acid group, and a diol
having an acid group. The polyol having no acid group contains a
polyether polyol having no acid group, and the percentage (% by
mole) constituted by a unit derived from the polyether polyol
having no acid group with respect to all the units derived from the
polyol having no acid group is 80% by mole or more. The polyether
polyol has a number-average molecular weight of 450 or more and
4,000 or less. The ratio of the percentage (% by mole) of urethane
bonds in the polyurethane polymer to the percentage (% by mole) of
urea bonds in the polyurethane polymer is 85.0/15.0 or more and
100.0/0 or less. The diol having an acid group is at least one
selected from dimethylolpropionic acid and dimethylolbutanoic acid,
and the acid value of the polyurethane polymer resulting from the
unit(s) derived from the diol having an acid group is 40 mgKOH/g or
more and 140 mgKOH/g or less.
Advantageous Effects of Invention
[0013] The present invention can provide an ink jet ink that
produces an image having high optical density, scratch resistance,
and highlighter resistance, has excellent ink ejection stability,
and can reduce image deflection caused by face wetting. The present
invention can also provide an ink cartridge containing an ink
according to an embodiment of the present invention and an ink jet
recording method.
DESCRIPTION OF EMBODIMENTS
[0014] The present invention will be described in detail with
reference to the following embodiments. An ink jet ink (hereinafter
referred to simply as an "ink") according to an embodiment of the
present invention contains a polyurethane polymer and a
self-dispersing pigment. The polyurethane polymer has units derived
from a polyisocyanate, a polyol having no acid group, and at least
one selected from dimethylolpropionic acid and dimethylolbutanoic
acid. The polyol having no acid group contains a polyether polyol
having no acid group, and the percentage (% by mole) constituted by
a unit derived from the polyether polyol having no acid group with
respect to all the units derived from the polyol having no acid
group is 80% by mole or more. The polyether polyol has a
number-average molecular weight of 450 or more and 4,000 or less.
The ratio of the percentage (% by mole) of urethane bonds in the
polyurethane polymer to the percentage (% by mole) of urea bonds in
the polyurethane polymer is 85.0/15.0 or more and 100/0 or less.
The acid value of the polyurethane polymer resulting from the
unit(s) derived from the at least one selected from
dimethylolpropionic acid and dimethylolbutanoic acid is 40 mgKOH/g
or more and 140 mgKOH/g or less.
[0015] The present inventors studied various pigment inks
containing a polyurethane polymer. In accordance with routine
procedures, in order to improve ink ejection stability,
polyurethane polymers having a high acid value or high
hydrophilicity were studied. As a result, it was found that some
polyurethane polymers provided markedly poor image fastness
(scratch resistance and highlighter resistance). As a result of
extensive studies, the present inventors found that the compounds
constituting the polyurethane polymer are greatly responsible for
the poor image fastness. The details are described below.
[0016] The polyurethane polymer is mainly composed of two segments:
a hard segment and a soft segment. The hard segment is mainly
composed of a polyisocyanate, a short-chain diol, and a chain
extension agent. The soft segment is mainly composed of a polyol.
The hard segment substantially contributes to high strength, while
the soft segment substantially contributes to flexibility. A micro
phase separation structure of the two segments can impart high
strength and flexibility, that is, high elasticity to a film of the
polyurethane polymer. Such film characteristics are closely related
to image fastness.
[0017] As described above, a hydrophilic polyurethane polymer is
generally obtained by increasing the acid value of the polyurethane
polymer. The acid value of the polyurethane polymer depends
substantially on the number of units derived from a compound having
an acid group in the polyurethane polymer. Thus, in order to
increase the acid value of the polyurethane polymer, the amount of
compound having an acid group used in the synthesis of the
polyurethane polymer must be increased. In general, the compound
having an acid group for use in the synthesis of the polyurethane
polymer may be (a) a polyol having an acid group or (b) a diol
having an acid group.
[0018] The (a) polyol having an acid group may be an acid-modified
polyol, such as a carboxylic-acid-modified polycaprolactone diol.
However, it was found that the synthesis of the polyurethane
polymer only using a polyol having an acid group as a compound
having an acid group results in marked decreases in the scratch
resistance and highlighter resistance of an image. This phenomenon
occurred not only in the case of high acid values but also in the
case of low acid values, that is, in the case that the amount of
polyol having an acid group was small. This is probably because the
polyurethane polymer synthesized using a polyol having an acid
group has the acid group in the soft segment and consequently has a
poor balance between strength and flexibility. Thus, it was found
that even when a polyurethane polymer synthesized only using a
polyol having an acid group as a compound having an acid group is
used in an ink, high ink ejection stability and image fastness
cannot be achieved.
[0019] The (b) diol having an acid group may be dimethylolpropionic
acid (hereinafter referred to as DMPA) or dimethylolbutanoic acid
(hereinafter referred to as DMBA). An increase in the amount of
DMPA or DMBA to increase the acid value of the polyurethane polymer
results in an increase in the number of hydroxy groups. Thus, an
increase in the amount of DMPA or DMBA used must be compensated for
by a relative decrease in the amount of polyol component, which has
a hydroxy group reactive with an isocyanate like DMPA or DMBA. This
decreases the number of soft segments, reduces the flexibility of
the polyurethane polymer, and increases the rigidity of the
resulting polyurethane polymer film, thus lowering image fastness.
Thus, it was found that use of a polyurethane polymer having a high
acid value due to a diol having an acid group, such as DMPA or
DMBA, in an ink can improve ink ejection stability but lowers image
fastness.
[0020] The present inventors found that a factor in the markedly
poor image fastness by the use of a polyurethane polymer having a
high acid value or high hydrophilicity is greatly related to the
structure of the polyurethane polymer. The present inventors also
found that the polyurethane polymer must be designed particularly
in terms of the two segment structures, the hard segment and the
soft segment, which are characteristic of the polyurethane polymer,
rather than changing the hydrophilicity and hydrophobicity of the
polyurethane polymer with respect to its acid value.
[0021] In consideration of these results, the present inventors
examined various polyurethane polymers and found that it is
important to use at least one diol having an acid group selected
from DMPA and DMBA as a compound having an acid group used in the
synthesis of the polyurethane polymer. It is also important that
the acid value of the polyurethane polymer resulting from the
unit(s) derived from the diol having an acid group is 40 mgKOH/g or
more and 140 mgKOH/g or less and that a polyether polyol having no
acid group and a number-average molecular weight of 450 or more and
4,000 or less is used as a polyol. The reasons for these are
described below in detail.
[0022] In general, a polyester polyol, a polyether polyol, a
polycarbonate diol, or a polycaprolactone polyol is used as a
polyol in the synthesis of the polyurethane polymer. Among these, a
polyether polyol is very flexible. Thus, even when a diol having an
acid group is used in the synthesis of the polyurethane polymer, a
soft segment composed of a polyether polyol rarely causes a
reduction in flexibility due to a decrease in the number of soft
segments as described above. Thus, even with a somewhat high acid
value, the polyurethane polymer can have high flexibility. The
present inventors found that when the acid value of the
polyurethane polymer resulting from the unit(s) derived from the
diol having an acid group is 140 mgKOH/g or less the polyurethane
polymer can have high flexibility and excellent image fastness. On
the other hand, when the acid value of the polyurethane polymer
resulting from the unit(s) derived from the diol having an acid
group is less than 40 mgKOH/g, the prerequisite ink ejection
stability may be lowered. Thus, when a polyether polyol and a diol
having an acid group are used, the acid value of the polyurethane
polymer resulting from the unit(s) derived from the diol having an
acid group must be 40 mgKOH/g or more and 140 mgKOH/g or less.
[0023] It is also found that the flexibility of the polyether
polyol also greatly depends on its molecular weight. The present
inventors studied the molecular weight of the polyether polyol and
found that the polystyrene-equivalent number-average molecular
weight of the polyether polyol must be 450 or more and 4,000 or
less as determined by gel permeation chromatography (GPC). When the
polyether polyol has a molecular weight of less than 450, the
polyether polyol has low flexibility because of its short molecular
chain, and the resulting polyurethane polymer has low flexibility
relative to its strength. On the other hand, when the polyether
polyol has a molecular weight of more than 4,000, the polyether
polyol has excessively high flexibility because of its long
molecular chain, and the resulting polyurethane polymer has low
strength relative to its flexibility. In both cases, the
polyurethane polymer has a poor balance between strength and
flexibility, resulting in low scratch resistance and highlighter
resistance of an image.
[0024] The polyurethane polymer described above can be used to
significantly improve ink ejection stability and image fastness
(scratch resistance and highlighter resistance). However, the
present inventors found that the ejection of such a polyurethane
polymer through an ink jet recording head may cause another problem
of face wetting, which results in image deflection.
[0025] The present inventors examined various polyurethane polymers
and found that a polyurethane polymer having a larger number of
urea bonds more frequently causes face wetting. This is probably
because two N--H bonds of one urea bond interact with a face to
deposit the polyurethane polymer on the face.
[0026] On the basis of these findings, polyurethane polymers having
different molar ratios of the urethane bond to the urea bond were
examined for image deflection. As a result, it was found that a
polyurethane polymer that has the structure described above and a
smaller number of urea bonds less frequently causes image
deflection. More specifically, the ratio of the percentage (% by
mole) of the urethane bond to the percentage (% by mole) of the
urea bond in the polyurethane polymer must be 85.0/15.0 or more and
100.0/0 or less. A method for controlling the molar ratio will be
described below.
[0027] It was also found that use of a polyurethane polymer that
has a smaller number of urea bonds can further improve ink ejection
stability. This is probably because a decrease in the number of
hydrogen bonds formed by the urea bonds results in weaker
intramolecular or intermolecular interaction of the polymer and an
increase in the degree of freedom of the polymer molecule in the
ink, which facilitates the addition of a water molecule to an acid
group of the polymer molecule, thereby increasing hydrophilicity.
Although the urethane bond can also form the hydrogen bond, its
hydrogen bond strength is smaller than that of the urea bond. Thus,
the urethane bond does not prevent the addition of water molecule
to an acid group of the polymer molecule.
[0028] In addition to the use of such a polyurethane polymer that
has a smaller number of urea bonds, use of a self-dispersing
pigment can achieve high optical density, as well as high scratch
resistance and highlighter resistance of an image. The present
inventors believe the reason for that is as follows.
[0029] In general, self-dispersing pigments have a higher pigment
aggregation speed associated with water evaporation than
polymer-dispersed pigments. Thus, a self-dispersing pigment
aggregates rapidly on a recording medium. Pigment particles
remaining on the surface of the recording medium can yield a high
optical density.
[0030] A urea bond of the polyurethane polymer can easily form a
hydrogen bond with a functional group of a self-dispersing pigment
particle. The polyurethane polymer interacting with the surface of
the self-dispersing pigment particle can function as a polymer
dispersant and stabilize the dispersion of the self-dispersing
pigment. This prevents rapid aggregation of the self-dispersing
pigment on the recording medium. Thus, high optical density
intrinsic to the self-dispersing pigment cannot be achieved. Use of
a polyurethane polymer that has a smaller number of urea bonds can
reduce the interaction between the surface of a pigment particle
and the polyurethane polymer, thus allowing rapid aggregation of
the pigment on the recording medium. The self-dispersing pigment
can therefore exhibit its intrinsic high optical density.
[0031] Thus, these constituents can synergistically produce their
effects to achieve the advantages of the present invention.
Ink Jet Ink
[0032] The components of an ink jet ink according to an embodiment
of the present invention will be described below.
Polyurethane Polymer
[0033] A polyurethane polymer for use in an ink according to an
embodiment of the present invention will be described below in
detail.
Polyisocyanate
[0034] The term "polyisocyanate", as used herein, refers to a
compound having two or more isocyanate groups. Examples of the
polyisocyanate for use in an embodiment of the present invention
include, but are not limited to, aliphatic polyisocyanates,
alicyclic polyisocyanates, aromatic polyisocyanates, and
araliphatic polyisocyanates. The percentage (% by mass) of the
unit(s) derived from the polyisocyanate in the polyurethane polymer
may be 10% by mass or more and 80% by mass or less.
[0035] Examples of the aliphatic polyisocyanate include, but are
not limited to, tetramethylene diisocyanate, dodecamethylene
diisocyanate, hexamethylene diisocyanate,
2,2,4-trimethylhexamethylene diisocyanate,
2,4,4-trimethylhexamethylene diisocyanate, lysine diisocyanate,
2-methylpentane-1,5-diisocyanate, and
3-methylpentane-1,5-diisocyanate. Examples of the alicyclic
polyisocyanate include, but are not limited to, isophorone
diisocyanate, hydrogenated xylylene diisocyanate,
4,4-dicyclohexylmethane diisocyanate, 1,4-cyclohexane diisocyanate,
methylcyclohexylene diisocyanate, and
1,3-bis(isocyanatomethyl)cyclohexane. Examples of the aromatic
polyisocyanate include, but are not limited to, tolylene
diisocyanate, 2,2-diphenylmethane diisocyanate, 2,4-diphenylmethane
diisocyanate, 4,4-diphenylmethane diisocyanate, 4,4-dibenzyl
diisocyanate, 1,5-naphthylene diisocyanate, xylylene diisocyanate,
1,3-phenylene diisocyanate, and 1,4-phenylene diisocyanate.
Examples of the araliphatic polyisocyanate include, but are not
limited to, dialkyldiphenylmethane diisocyanate,
tetraalkyldiphenylmethane diisocyanate, and
alpha,alpha,alpha,alpha-tetramethylxylylene diisocyanate. These
polyisocyanates may be used alone or in combination. Among these
polyisocyanates, hexamethylene diisocyanate may be used in an
embodiment of the present invention. Hexamethylene diisocyanate may
be used in combination with another polyisocyanate. The reason for
this is described below.
[0036] Hexamethylene diisocyanate (hereinafter referred to as HDI)
has a straight chain structure, small steric hindrance, and high
molecular symmetry. In a polyurethane polymer synthesized using
HDI, therefore, HDI molecules tend to gather because of hydrogen
bonds formed by urethane bonds. Thus, in the polyurethane polymer
synthesized using HDI, hard segments containing the polyisocyanate
are localized. This tends to result in micro phase separation in
which the hard segments are present in a continuous soft segment to
form a sea-island structure, thus markedly increasing the
flexibility of the polyurethane polymer. In contrast, a
polyisocyanate that has an intramolecular branched or ring
structure has large steric hindrance and rarely forms a hydrogen
bond. However, an interaction between the ring structures and
hydrophobic interaction increase the number of hard segments and
markedly increase the strength of the polyurethane polymer. Thus,
use of HDI and another polyisocyanate in combination imparts
flexibility due to HDI and strength due to that other
polyisocyanate to the polyurethane polymer, thereby achieving
higher scratch resistance and highlighter resistance of an
image.
[0037] The percentage (% by mole) constituted by the unit(s)
derived from HDI with respect to all the units derived from the
polyisocyanate in the polyurethane polymer may be 10% by mole or
more and 90% by mole or less. The balance of the effect of
improving strength and flexibility between HDI and the
polyisocyanate other than HDI is satisfactory within this range.
This further improves the scratch resistance and highlighter
resistance of an image.
Polyether Polyol Having No Acid Group
[0038] As described above, the polyether polyol having no acid
group for use in an embodiment of the present invention has a
polystyrene-equivalent number-average molecular weight of 450 or
more and 4,000 or less as determined by GPC. The percentage (% by
mass) of the unit(s) derived from the polyether polyol having no
acid group in the polyurethane polymer may be 0.1% by mass or more
and 80.0% by mass or less. In one embodiment of the present
invention, the polyether polyol having no acid group may be used in
combination with another polyol having no acid group other than the
polyether polyol to synthesize the polyurethane polymer. In this
case, the percentage (% by mole) constituted by the unit(s) derived
from the polyether polyol having no acid group with respect to all
the units derived from the polyol having no acid group in the
polyurethane polymer may be 80% by mole or more and 100% by mole or
less. In particular, no castor-oil-modified polyol may be used in
view of ink ejection stability.
[0039] Examples of the polyether polyol include, but are not
limited to, poly(alkylene glycol)s and addition polymers of
alkylene oxides and dihydric alcohols or at least trivalent
polyhydric alcohols. Examples of the poly(alkylene glycol)s
include, but are not limited to, poly(ethylene glycol),
poly(propylene glycol), poly(tetramethylene glycol),
poly(1,2-butylene glycol), poly(1,3-butylene glycol), and ethylene
glycol-propylene glycol copolymers. Examples of the dihydric
alcohols include, but are not limited to, hexamethylene glycol,
tetramethylene glycol, ethylene glycol, diethylene glycol,
propylene glycol, dipropylene glycol, 1,3-butanediol,
1,4-butanediol, 4,4-dihydroxyphenylpropane, and
4,4-dihydroxyphenylmethane. Examples of the at least trivalent
polyhydric alcohols include, but are not limited to, glycerin,
trimethylolpropane, 1,2,5-hexanetriol, 1,2,6-hexanetriol, and
pentaerythritol. Examples of the alkylene oxides include, but are
not limited to, ethylene oxide, propylene oxide, butylene oxide,
and alpha-olefin oxides. These polyether polyols may be used alone
or in combination.
[0040] In one embodiment of the present invention, the polyether
polyol having no acid group may contain at least one selected from
poly(ethylene glycol), poly(propylene glycol), poly(1,2-butylene
glycol), and poly(1,3-butylene glycol). Use of these polyether
polyols can increase the strength, flexibility, and hydrophilicity
of the polyurethane polymer, thereby further improving the scratch
resistance and highlighter resistance of an image and ink ejection
stability. The percentage (% by mole) constituted by the unit(s)
derived from poly(ethylene glycol), poly(propylene glycol),
poly(1,2-butylene glycol), and poly(1,3-butylene glycol) with
respect to all the units derived from the polyether polyol in the
polyurethane polymer may be 80% by mole or more and 100% by mole or
less. In particular, the polyether polyol having no acid group may
contain poly(propylene glycol). Use of poly(propylene glycol) can
improve the balance between the strength and the flexibility of the
polyurethane polymer film.
Diol Having Acid Group
[0041] A polyurethane polymer for use in an ink according to an
embodiment of the present invention has a unit derived from at
least one selected from DMPA and DMBA as a diol having an acid
group. The diol having an acid group may be in the form of a salt
with an alkali metal, such as Li, Na, or K, or an organic amine,
such as ammonia or dimethylamine. These diols may be used alone or
in combination. The percentage (% by mass) of the unit(s) derived
from the diol having an acid group in the polyurethane polymer may
be 5.0% by mass or more and 40.0% by mass or less.
Chain Extension Agent
[0042] A chain extension agent is a compound that can react with a
residual isocyanate group of a polyisocyanate unit of a urethane
prepolymer. The residual isocyanate group is an isocyanate group
that did not form a urethane bond. In one embodiment of the present
invention, a chain extension agent may be used in the synthesis of
the polyurethane polymer provided that the molar ratio of the
urethane bond to the urea bond in the polyurethane polymer is
85.0/15.0 or more and 100.0/0 or less. Examples of the chain
extension agent include, but are not limited to, polyvalent amine
compounds, such as trimethylolmelamine and derivatives thereof,
dimethylolurea and derivatives thereof, dimethylolethylamine,
diethanolmethylamine, dipropanolethylamine, dibutanolmethylamine,
ethylenediamine, propylenediamine, diethylenetriamine,
hexylenediamine, triethylenetetramine, tetraethylenepentamine,
isophoronediamine, xylylenediamine, diphenylmethanediamine,
hydrogenated diphenylmethanediamine, and hydrazine, polyamide
polyamine, and polyethylene polyimine. Examples of the chain
extension agent also include, but are not limited to, ethylene
glycol, propylene glycol, 1,3-propanediol, 1,3-butanediol,
1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, neopentyl glycol,
diethylene glycol, triethylene glycol, tetraethylene glycol,
dipropylene glycol, tripropylene glycol, poly(ethylene glycol),
3-methyl-1,5-pentanediol, 2-butyl-2-ethyl-1,3-propanediol,
1,4-cyclohexanediol, 1,4-cyclohexanedimethanol, hydrogenated
bisphenol A, glycerin, trimethylolpropane, and pentaerythritol.
These chain extension agents may be used alone or in
combination.
Cross-Linker
[0043] A polyurethane polymer for use in an ink according to an
embodiment of the present invention may be a cross-linked
polyurethane polymer. The cross-linked polyurethane polymer may be
produced by using an at least trifunctional polyisocyanate, polyol,
or chain extension agent, which functions as a cross-linker.
[0044] The cross-linked polyurethane polymer is rich in the hard
segment of the micro phase separation structure of the polyurethane
polymer. This is because use of, for example, a trifunctional
cross-linker results in the formation of three urethane bonds per
cross-linker. This markedly increases the strength of the
polyurethane polymer. This also increases the number of adjacent
urethane bonds and accordingly the number of hydrogen bonds between
the urethane bonds. Consequently, the hard segments gather more
closely and easily undergo micro phase separation to form a
sea-island structure, maintaining high flexibility of the
polyurethane polymer. Thus, the cross-linked polyurethane polymer
has very high strength and high flexibility and improves the
scratch resistance and highlighter resistance of an image.
[0045] Examples of at least trifunctional compound that can be used
as a cross-linker in an embodiment of the present invention
include, but are not limited to, at least trifunctional
polyisocyanates, at least trifunctional polyols, and at least
trifunctional chain extension agents. The cross-linked polyurethane
polymer can be synthesized using at least one selected from the at
least trifunctional compounds. Examples of the at least
trifunctional polyisocyanates include, but are not limited to,
polyisocyanurates, adduct-type polyisocyanates, and biuret
polyisocyanates. Examples of the at least trifunctional polyols
include, but are not limited to, glycerin, trimethylolpropane,
1,2,5-hexanetriol, 1,2,6-hexanetriol, pentaerythritol,
polyoxypropylenetriol, and glycol adducts of the polyether polyols
described above. Examples of the at least trifunctional chain
extension agent include, but are not limited to,
trimethylolmelamine, diethylenetriamine, triethylenetetramine, and
tetraethylenepentamine. In particular, at least one selected from
glycerin, trimethylolpropane, pentaerythritol, and
polyoxypropylenetriol may be used.
Method for Determining Whether Cross-Linked Polyurethane Polymer or
Not
[0046] The present inventors found that whether the polyurethane
polymer is a cross-linked polyurethane polymer or not can be
determined by gel fraction. When a polyurethane polymer is
dissolved in a solvent, the gel fraction of the polyurethane
polymer is the ratio of the mass of residual gel (a cross-linked
structure remains as gel) to the mass of the polyurethane polymer
before dissolved in the solvent. The gel fraction can be measured
by the solubility of a polyurethane polymer film in a solvent and
is a measure of the degree of cross-linking. A polyurethane polymer
having a higher degree of cross-linking has a higher gel fraction.
In one embodiment of the present invention, the gel fraction is
measured by the following method to determine whether the
polyurethane polymer is a cross-linked polyurethane polymer or
not.
[0047] A film of a polyurethane polymer extracted by a method
described below is immersed in tetrahydrofuran (THF) at 23 degrees
Celsius for 24 hours. The mass (A) of a THF-insoluble fraction of
the polyurethane polymer film is measured and is divided by the
mass (B) of the polyurethane polymer film before immersion to
calculate a THF gel fraction (A/B.times.100). In one embodiment of
the present invention, a polyurethane polymer having a THF gel
fraction of 88% by mass or more and 100% by mass or less is
considered to be a cross-linked polyurethane polymer.
Molar Ratio of Urethane Bond to Urea Bond
[0048] As described above, the ratio of the percentage (% by mole)
of the urethane bond to the percentage (% by mole) of the urea bond
in the polyurethane polymer for use in an ink according to an
embodiment of the present invention is 85.0/15.0 or more and
100.0/0 or less. In one embodiment of the present invention, the
molar ratio of the urethane bond to the urea bond may be 85.0/15.0
or more and 98.5/1.5 or less. When the molar ratio of the urethane
bond to the urea bond is 98.5/1.5 or less, the scratch resistance
and highlighter resistance of an image are further improved.
[0049] In one embodiment of the present invention, the molar ratio
of the urethane bond to the urea bond of the polyurethane polymer
may be controlled by either of the following two methods.
[0050] In accordance with a first method, the amount of amine
compound used in the synthesis of the polyurethane polymer is
controlled. This is because the amine compound reacts with an
isocyanate group to form a urea bond. The amine compound may be an
amine chain extension agent. More specifically, the polyurethane
polymer may be synthesized by the following method. First,
polyurethane polymers are synthesized using different amounts of an
amine compound. The molar ratio of the urethane bond to the urea
bond of each of the polyurethane polymers is measured by the method
described below. On the basis of these results, the correlation
between the amount of amine compound used and the molar ratio of
the urethane bond to the urea bond is examined to determine the
amounts of raw materials for a polyurethane polymer having a
desired molar ratio of the urethane bond to the urea bond. The
reason that the correlation between the amount of amine compound
used and the molar ratio is examined in advance is as follows. Even
with the same amine compound, use of different types of other raw
materials may result in a change in the reaction rate or the like,
yielding polyurethane polymers having different molar ratios of the
urethane bond to the urea bond.
[0051] In accordance with a second method, the percentage of the
unreacted isocyanate group is controlled in phase inversion of the
polyurethane polymer to water. Water reacts with an isocyanate
group to form a urea bond. More specifically, the polyurethane
polymer is synthesized by the following method. First, the
percentage of the unreacted isocyanate group in the synthesis of
the polyurethane polymer is measured with a Fourier transform
infrared spectrophotometer (FT-IR). When the percentage of the
unreacted isocyanate group reaches the desired molar ratio of the
urethane bond to the urea bond, ion-exchanged water is added to the
reaction system. For example, in the synthesis of a polyurethane
polymer having a molar ratio of the urethane bond to the urea bond
of 95.0/5.0, ion-exchanged water is added when the percentage of
the unreacted isocyanate group is 5% by mole. The percentage of the
unreacted isocyanate group may be controlled by the reaction time
or the initial amount of polyisocyanate. In the examples described
below, the molar ratio of the urethane bond to the urea bond of the
polyurethane polymer was controlled by the second method.
Characteristics of Polyurethane Polymer
[0052] The percentage (% by mass) of the polyurethane polymer for
use in an ink according to an embodiment of the present invention
may be 0.1% by mass or more and 10.0% by mass or less of the total
mass of the ink Less than 0.1% by mass of the polyurethane polymer
may have an insufficient effect of improving the scratch resistance
and highlighter resistance of an image. More than 10.0% by mass of
the polyurethane polymer may have an insufficient effect of
improving ink ejection stability. The ink may further contain
another polymer without compromising the advantages of the present
invention.
[0053] The ratio of the polyurethane polymer content (% by mass) of
the ink to the self-dispersing pigment content (% by mass) based on
the total mass of the ink described below may be 0.05 or more and
2.00 or less. A mass ratio of less than 0.05 may result in an
insufficient effect of improving the scratch resistance and
highlighter resistance of an image. When the mass ratio is more
than 2.00, this may result in an insufficient effect of improving
ink ejection stability.
[0054] A polyurethane polymer for use in an ink according to an
embodiment of the present invention may have a
polystyrene-equivalent weight-average molecular weight (Mw) of more
than 30,000 and 150,000 or less as determined by GPC. When the
polystyrene-equivalent weight-average molecular weight (Mw) is
30,000 or less, the polyurethane polymer may have low strength and
an insufficient effect of improving the scratch resistance and
highlighter resistance of an image. When the polystyrene-equivalent
weight-average molecular weight (Mw) is more than 150,000, the ink
tends to have a high viscosity, and this may result in an
insufficient effect of improving ink ejection stability.
[0055] A polyurethane polymer for use in an ink according to an
embodiment of the present invention may have an acid value of 40
mgKOH/g or more and 150 mgKOH/g or less. As described above, the
acid value of the polyurethane polymer resulting from the unit(s)
derived from the diol having an acid group must be 40 mgKOH/g or
more and 140 mgKOH/g or less. The acid value of the polyurethane
polymer resulting from the unit(s) derived from the diol having an
acid group may be 45 mgKOH/g or more and 100 mgKOH/g or less.
Method for Synthesizing Polyurethane Polymer
[0056] A method for synthesizing a polyurethane polymer according
to an embodiment of the present invention may be any known method,
including the following method. A polyisocyanate, a polyol having
no acid group, and a diol having an acid group are allowed to react
to synthesize a urethane prepolymer having a terminal isocyanate
group. An acid group of the urethane prepolymer is then neutralized
with a neutralizing agent. The neutralized urethane prepolymer is
further allowed to react in an aqueous solution containing a chain
extension agent or a cross-linker. An organic solvent remaining in
the system, if any, may be removed.
[0057] The present inventors found that, when two polyisocyanates
(a first polyisocyanate and a second polyisocyanate) are used to
synthesize a polyurethane polymer having a decreased number of urea
bonds, a high-molecular-weight polyurethane polymer can be produced
by the following method while the molar ratio of the urethane bond
to the urea bond is controlled. More specifically, the first
polyisocyanate, a polyol having no acid group, and a diol having an
acid group are allowed to react. The reaction is continued until
the percentage of the unreacted isocyanate group in the reaction
system becomes zero as measured with an FT-IR, yielding a
prepolymer solution. This prepolymer contains no isocyanate group
of the first polyisocyanate. The second polyisocyanate is added to
the prepolymer solution and is allowed to react until the
percentage of the unreacted isocyanate group in the reaction system
reaches a desired value as measured with an FT-IR. A chain
extension agent or a cross-linker is then added to the prepolymer
solution and is allowed to react to yield a polyurethane polymer
solution. The phase inversion of the polyurethane polymer solution
to water yields a polyurethane polymer dispersion having a desired
molar ratio of the urethane bond to the urea bond. In this
synthesis method, when the first polyisocyanate is isophorone
diisocyanate, the scratch resistance and highlighter resistance of
an image are improved. Whether a polyurethane polymer is
synthesized by this synthesis method or not may be determined by
the following method. When the molar ratio X of the urethane bond
formed between the first polyisocyanate and the diol having an acid
group to the first polyisocyanate is larger than the molar ratio Y
of the urethane bond formed between the second polyisocyanate and
the diol having an acid group to the second polyisocyanate, the
polyurethane polymer is considered to be synthesized by the
synthesis method described above. X and Y can be determined by
nuclear magnetic resonance (NMR) as described below.
Method for Analyzing Polyurethane Polymer
[0058] The composition, the molecular weight, and the acid value of
the resulting polyurethane polymer can be analyzed by examining the
sediment and the supernatant liquid after the centrifugation of the
ink Since the pigment is insoluble in organic solvents, the
polyurethane polymer can also be isolated by solvent extraction.
Although the ink itself can be analyzed, the isolation of the
polyurethane polymer can improve the accuracy of measurement. More
specifically, after the centrifugation of the ink at 80,000 rpm,
the supernatant liquid is precipitated with hydrochloric acid and
is dried.
(1) Polyurethane Polymer Composition
[0059] The dried precipitate is dissolved in deuterated dimethyl
sulfoxide (deuterated DMSO) and is subjected to proton nuclear
magnetic resonance (.sup.1H-NMR). The types of the polyisocyanate,
the polyether polyol having no acid group, and the diol having an
acid group can be determined by the peak positions of the proton
nuclear magnetic resonance and the measurement of the dried
precipitate by pyrolysis-gas chromatography. The component ratio
can be calculated from the ratio of the integral values of chemical
shift peaks. The percentage constituted by the unit(s) derived from
HDI with respect to all the units derived from the polyisocyanate
in the polyurethane polymer can be calculated by this method.
(2) Method for Measuring Molar Ratio of Urethane Bond to Urea Bond
of Polyurethane Polymer
[0060] The molar ratio of the urethane bond to the urea bond of the
polyurethane polymer can be determined by the ratio of the integral
value of the peaks of the urethane bond to the integral value of
the peaks of the urea bond of the polyurethane polymer precipitate
dissolved in deuterated DMSO measured by carbon nuclear magnetic
resonance (.sup.13C-NMR). The peak positions of the urethane bond
and the urea bond depend on the types of raw material compounds of
the polyurethane polymer (a polyisocyanate, a polyether polyol
having no acid group, and a diol having an acid group). Thus, the
peak positions of the urethane bond and the urea bond for the raw
material compounds of the polyurethane polymer must be examined by
the following method.
[0061] First, the raw material compounds of the polyurethane
polymer (a polyisocyanate, a polyether polyol having no acid group,
and a diol having an acid group) are prepared. (i) A reaction
product between the polyisocyanate and the polyether polyol having
no acid group, (ii) a reaction product between the polyisocyanate
and the diol having an acid group, and (iii) a reaction product
between the polyisocyanate and water are obtained. Each of the
products is then dried, is dissolved in deuterated DMSO, and is
subjected to .sup.13C-NMR measurement. The peak position of the
urethane bond in each of the reaction products can be identified
from the results for (i) and (ii). The peak position of the urea
bond in each of the reaction products can be identified from the
result for (iii). For example, when the polyisocyanate is
isophorone diisocyanate, the peak position of the urethane bond is
approximately 155 ppm, and the peak position of the urea bond is
approximately 158 ppm.
(3) Method for Measuring Acid Value of Polyurethane Polymer
[0062] The acid value of the polyurethane polymer can be measured
by titrimetry. In the examples described below, the acid value of
the polyurethane polymer was measured by potentiometric titration
of the polymer dissolved in THF with an automatic potentiometric
titrator AT510 (manufactured by Kyoto Electronics Manufacturing
Co., Ltd.) using a potassium hydroxide-ethanol titrant.
[0063] The acid value of the diol having an acid group (DMPA or
DMBA) can be measured by the following method. First, a
polyurethane polymer precipitate dissolved in deuterated DMSO is
subjected to .sup.13C-NMR measurement. The molar ratio of DMPA or
DMBA to another compound having an acid group (for example, acrylic
acid) is calculated by the ratio of the peak of the quaternary
carbon atom of DMPA or DMBA to the integral value of the peak of an
acid group of that other compound. The acid value of the
polyurethane polymer is multiplied by the molar ratio of DMPA or
DMBA to calculate the acid value of the diol having an acid group,
DMPA or DMBA. The peak position of the quaternary carbon atom of
DMPA or DMBA is approximately 65 or 60 ppm, respectively. When no
compound having an acid group other than DMPA or DMBA is used, the
acid value of the diol having an acid group can be measured by the
titrimetry.
(4) Method for Measuring Average Molecular Weight of Polyurethane
Polymer
[0064] The average molecular weight of the polyurethane polymer can
be measured by GPC. In GPC measurement, an apparatus Alliance GPC
2695 (manufactured by Waters), four columns of Shodex KF-806M
(manufactured by Showa Denko K.K.) in series, and a RI (refractive
index) detector were used. The average molecular weight was
calculated using polystyrene standard samples PS-1 and PS-2
(manufactured by Polymer Laboratories).
(5) Method for Measuring Number-Average Molecular Weight of
Polyether Polyol Having No Acid Group
[0065] The polyurethane polymer dissolved in deuterated DMSO can be
subjected to carbon nuclear magnetic resonance (.sup.13C-NMR) to
calculate the number of polyether polyol units having no acid group
and the number-average molecular weight of the polyether
polyol.
Self-Dispersing Pigment
[0066] An ink according to an embodiment of the present invention
contains a self-dispersing pigment in which at least one
hydrophilic group is bonded to the surface of the pigment particle
directly or through another atomic group. The at least one
hydrophilic group in the ink may be partly or entirely
dissociated.
[0067] Examples of the pigment for use in an ink according to an
embodiment of the present invention include, but are not limited
to, inorganic and organic pigments, such as carbon black. Any known
pigment can be used in an ink jet ink according to an embodiment of
the present invention. The present inventors found that the
polyurethane polymer is physically adsorbed on inorganic pigments
more easily than organic pigments. Use of inorganic pigments
therefore more effectively improves the scratch resistance and
highlighter resistance of an image. The self-dispersing pigment
content (% by mass) of the ink is 0.1% by mass or more and 15.0% by
mass or less, preferably 1.0% by mass or more and 8.0% by mass or
less, of the total mass of the ink. A self-dispersing pigment
content of less than 1.0% by mass may result in insufficient
optical density. A self-dispersing pigment content of more than
8.0% by mass may result in poor ink jet characteristics, such as
sticking resistance.
[0068] Examples of the self-dispersing pigment include, but are not
limited to, pigments having a hydrophilic group on the surface of
the pigment particle (self-dispersing pigments modified with
hydrophilic groups) and pigments having a polymer organic group on
the surface of the pigment particle (polymer-attached
self-dispersing pigments). Use of the self-dispersing pigment can
obviate the necessity for the addition of a dispersant to disperse
the pigment in the ink or can reduce the amount of dispersant. In
one embodiment of the present invention, the self-dispersing
pigment modified with hydrophilic groups can be used. The pigment
can be self-dispersing carbon black. Self-dispersing carbon black
can promote a change in the state of the ink (an increase in
viscosity, the association or aggregation of a coloring material,
or the like) as the ink dries on a recording medium. Thus,
self-dispersing carbon black is very effective in achieving high
optical density.
Self-Dispersing Pigments Modified with Hydrophilic Groups
[0069] The hydrophilic group on the surface of the pigment particle
may be an anionic group, such as --COOM, --SO.sub.3M, --PO.sub.3HM,
or --PO.sub.3M.sub.2, wherein "M" denotes a hydrogen atom, an
alkali metal, ammonium, or an organic ammonium. When "M" is an
alkali metal, such as lithium, sodium, or potassium, the ink has
excellent ejection stability. The hydrophilic group may be bonded
to the surface of the pigment particle directly or via another
atomic group (--R--). The atomic group (--R--) may be a linear or
branched alkylene group having 1 to 12 carbon atoms, an arylene
group, such as a phenylene group or a naphthylene group, an amide
group, a sulfonyl group, an amino group, a carbonyl group, an ester
group, or an ether group, or a combination thereof.
Polymer-Attached Self-Dispersing Pigment
[0070] A polymer used in a polymer-attached self-dispersing pigment
may be any known polymer used in ink jet inks, for example, an
acrylic acid polymer. A polymer attached to the pigment preferably
has a polystyrene-equivalent weight-average molecular weight in the
range of 1,000 to 12,000, more preferably 3,000 to 8,000, as
determined by GPC. The polymer preferably has an acid value of 50
mgKOH/g or more and 300 mgKOH/g or less, more preferably 120
mgKOH/g or more and 250 mgKOH/g or less.
Aqueous Medium
[0071] An ink according to an embodiment of the present invention
may contain water or an aqueous medium, such as a mixed solvent of
water and a water-soluble organic solvent. The amount (% by mass)
of water-soluble organic solvent in the ink may be 3.0% by mass or
more and 50.0% by mass or less of the total mass of the ink. The
water-soluble organic solvent may be any known solvent generally
used in ink jet inks. Examples of the water-soluble organic solvent
include, but are not limited to, alkyl alcohols having 1 to 4
carbon atoms, amides, ketones, keto-alcohols, ethers, poly(alkylene
glycol)s, glycols, alkylene glycols in which the alkylene group has
2 to 6 carbon atoms, polyhydric alcohols, alkyl ether acetates,
alkyl ethers of polyhydric alcohols, nitrogen-containing compounds,
and sulfur-containing compounds. These water-soluble organic
solvents may be used alone or in combination. Water can be
deionized water (ion-exchanged water). The water content (% by
mass) of the ink may be 50.0% by mass or more and 95.0% by mass or
less of the total mass of the ink. The ink viscosity at 25 degrees
Celsius may be 6 cps or less. The ink viscosity can be controlled
through the composition and the amount of the aqueous medium. An
ink viscosity of more than 6 cps at 25 degrees Celsius may result
in an insufficient effect of improving ink ejection stability.
Salt
[0072] An ink according to an embodiment of the present invention
can also contain a salt. The term "salt", as used herein, refers to
a compound formed by neutralization between a cation and an anion.
The salt in the ink may be partly or entirely dissociated. The
expression "contain a salt" includes the presence of a dissociated
salt. The addition of a salt to an ink according to an embodiment
of the present invention can promote the agglomeration of pigment
on a recording medium and significantly improve optical
density.
[0073] Examples of the salt for use in an ink according to an
embodiment of the present invention include, but are not limited
to, combinations of the following cations and anions. Specific
examples of the cations include, but are not limited to, monovalent
metal ions, such as Li.sup.+, Na.sup.+, and K.sup.+, ammonium ion,
and organic ammonium ions. Examples of the anions include, but are
not limited to, Cl.sup.-, Br.sup.-, I.sup.-, ClO.sup.-, ClO.sup.2-,
ClO.sup.3-, ClO.sup.4-, NO.sup.2-, NO.sup.3-, SO.sub.4.sup.2-,
CO.sub.3.sup.2-, HCOO.sup.-, CH.sub.3COO.sup.-,
C.sub.2H.sub.4(COO.sup.-).sub.2, C.sub.6H.sub.5COO.sup.-, and
C.sub.6H.sub.4(COO.sup.-).sub.2.
[0074] The salt content (% by mass) of an ink according to an
embodiment of the present invention may be 0.01% by mass or more
and 10.0% by mass or less of the total mass of the ink. A salt
content of less than 0.01% by mass may result in an insufficient
effect of improving optical density. A salt content of more than
10.0% by mass may result in an insufficient effect of improving ink
storage stability.
Other Additive Agents
[0075] In addition to the components described above, an ink
according to an embodiment of the present invention may further
contain a water-soluble organic compound that is solid at normal
temperature, for example, a polyhydric alcohol, such as
trimethylolpropane or trimethylolethane, urea, or a urea
derivative, such as ethylene urea. An ink according to an
embodiment of the present invention may also contain an additive
agent, such as a polymer other than the polyurethane polymer, a
surfactant, a pH-adjusting agent, an anticorrosive, a preservative,
a fungicide, an antioxidant, a reduction inhibitor, an evaporation
accelerator, and/or a chelator. In the case that the ink contains a
polymer other than the polyurethane polymer, the total polymer
content of the ink may be 0.01% by mass or more and 10.00% by mass
or less of the total mass of the ink.
Ink Cartridge
[0076] An ink cartridge according to an embodiment of the present
invention includes an ink storage portion for storing an ink
according to an embodiment of the present invention. The ink
storage portion may include an ink chamber and a chamber for
housing a negative-pressure-generating member. The ink chamber can
store liquid ink. The negative-pressure-generating member can store
ink by the action of a negative pressure. Alternatively, an ink
cartridge according to an embodiment of the present invention may
include no ink chamber and include an ink storage portion that
includes a negative-pressure-generating member for storing the
whole ink. Alternatively, an ink cartridge according to an
embodiment of the present invention may include an ink storage
portion and a recording head.
Ink Jet Recording Method
[0077] An ink jet recording method according to an embodiment of
the present invention involves ejecting an ink according to an
embodiment of the present invention from an ejection port of a
recording head onto a recording medium by an ink jet method in
response to recording signals. The ink may be ejected from an
ejection port of a recording head by the action of thermal energy.
In one embodiment of the present invention, the face of the
recording head may be subjected to water-repellent finishing. The
face of the recording head may be subjected to water-repellent
finishing by any method. For example, the face of the recording
head may be treated with a water repellent made of a silicone
material or a fluorinated material. Examples of the water repellent
include, but are not limited to, KP-801 (manufactured by Shin-Etsu
Chemical Co., Ltd.), Defensa (manufactured by DIC Corp.), Cytop
CTX-105, 805 (manufactured by Asahi Glass Co., Ltd.), and Teflon
(registered trademark) AF (manufactured by DuPont). A
fluorine-containing silane compound may also be used as a water
repellent. The term "recording", as used herein, includes recording
on a recording medium with an ink according to an embodiment of the
present invention or printing on a substrate having little
permeability, such as a glass substrate, a plastic substrate, or a
non-permeable film, with an ink according to an embodiment of the
present invention. The recording medium may be plain paper or
glossy paper. Glossy paper includes a porous ink-absorbing layer on
a permeable support (such as paper). The porous ink-absorbing layer
contains an inorganic pigment and a binder. Use of an ink according
to an embodiment of the present invention on plain paper can
particularly have the advantages of the present invention.
[0078] An ink jet recording method according to an embodiment of
the present invention may include a process (A) of ejecting an ink
through an ink jet recording head onto a recording medium and a
process (B) of applying a liquid composition described below to the
recording medium such that the liquid composition at least partly
overlaps the ink. The process (A) may be followed or preceded by
the process (B). The same processes may be performed twice or more;
for example, the process (A), the process (B), and then the process
(A), or the process (B), the process (A), and then the process (B)
may be performed. In particular, performing the process (A) after
the process (B) has a large effect of improving the scratch
resistance and optical density of an image.
Liquid Composition
[0079] An ink according to an embodiment of the present invention
may be used in combination with a liquid composition that can
destabilize the dispersion of pigment in the ink and reduce the
solubility of the polyurethane polymer. The pigment reacts with a
reactant in the liquid composition to aggregate rapidly and remain
on the surface of a recording medium, thus increasing optical
density. The polyurethane polymer also reacts with a reactant in
the liquid composition. This reduces the solubility of the
polyurethane polymer and causes precipitation of the polyurethane
polymer. Thus, the polyurethane polymer is present in the vicinity
of the aggregated pigment and improves the scratch resistance and
highlighter resistance of an image. The phrase "destabilize the
dispersion of pigment in the ink", as used herein, means that
pigment particles aggregate as a result of a reduction in
electrostatic repulsion by which the pigment particles are
dispersed in the ink The phrase "reduce the solubility of the
polyurethane polymer", as used herein, means that the polyurethane
polymer, which has been dissolved (dispersed) in the ink by the
addition of a water molecule to an acid group of the polyurethane
polymer (hydration), is insolubilized by the prevention of
hydration.
[0080] In one embodiment of the present invention, the liquid
composition may be colorless, milk white, or white so as not to
affect an image recorded by the ink. Thus, the ratio Amax/Amin of
the maximum absorbance Amax to the minimum absorbance Amin in a
visible light wavelength in the range of 400 to 780 nm may be 1.0
or more and 2.0 or less. This means that the absorption peak is
substantially absent or very small in the visible light wavelength
region. A liquid composition according to an embodiment of the
present invention may contain no coloring material. The absorbance
may be measured after the liquid composition is diluted. This is
because the maximum absorbance Amax and the minimum absorbance Amin
of the liquid composition are proportional to the dilution ratio,
and therefore the Amax/Amin is independent of the dilution ratio.
The components of the liquid composition are described below.
Reactant
[0081] In one embodiment of the present invention, the liquid
composition may contain a reactant that can destabilize the
dispersion of pigment and reduce the solubility of the polyurethane
polymer in the ink. More specifically, the reactant may be a
polyvalent metal ion or an organic acid. The reactant content (% by
mass) of the liquid composition may be 3.0% by mass or more and
20.0% by mass or less of the total mass of the liquid composition.
Less than 3.0% by mass of the reactant cannot sufficiently
destabilize the pigment dispersion and may have an insufficient
effect of improving optical density. More than 20.0% by mass of the
reactant may cause the precipitation of the reactant and result in
poor ink jet characteristics.
Polyvalent Metal Ion
[0082] In one embodiment of the present invention, the polyvalent
metal ion of the liquid composition may be at least divalent.
Examples of the divalent metal ion include, but are not limited to,
alkaline-earth metals, such as beryllium, magnesium, calcium,
strontium, barium, and radium. Examples of at least trivalent metal
ion include, but are not limited to, aluminum, yttrium, zirconium,
iron, and other transition metal ions. In one embodiment of the
present invention, the polyvalent metal ion may be added in the
form of salt, such as hydroxide, chloride, or nitrate, to the
liquid composition. The polyvalent metal ion may also be a
dissociated ion.
[0083] In one embodiment of the present invention, at least one
selected from calcium ion, aluminum ion, and yttrium ion may be
used in terms of reactivity. In particular, calcium ion can be
used. A nitrate may be used in terms of the solubility of the salt.
One example of nitrate is calcium nitrate.
Organic Acid
[0084] The term "organic acid", as used herein, refers to an acid
of an organic compound. In one embodiment of the present invention,
the organic acid of the liquid composition may be a monocarboxylic
acid, such as formic acid, acetic acid, propionic acid, or butyric
acid; a dicarboxylic acid, such as oxalic acid, malonic acid,
succinic acid, or glutaric acid; or a hydroxycarboxylic acid, such
as malic acid or tartaric acid. In one embodiment of the present
invention, the organic acid may be added in the form of alkali
metal ion salt to the liquid composition or may also be a
dissociated ion.
[0085] When the reactant is an organic acid, the liquid composition
may have a pH of 3.5 or more and 5.5 or less. When the liquid
composition has a pH of less than 3.5, this may result in the acid
corrosion of a member of an ink jet recording apparatus. When the
liquid composition has a pH of more than 5.5, this may result in an
insufficient effect of improving the scratch resistance and
highlighter resistance of an image. The pH of the liquid
composition is measured at 25 degrees Celsius and can be measured
with a common pH meter. When the reactant is an organic acid, the
liquid composition may have pH-buffering action. The sentence "the
liquid composition has pH-buffering action", as used herein, means
that an equivalent mixture of the liquid composition and the ink
has substantially the same pH as the liquid composition. The phrase
"substantially the same pH as the liquid composition", as used
herein, refers to a pH change of less than 0.1.
Aqueous Medium and Another Additive Agent
[0086] The liquid composition may contain water or an aqueous
medium, such as a mixed solvent of water and a water-soluble
organic solvent. The amount (% by mass) of water-soluble organic
solvent in the liquid composition may be 3.0% by mass or more and
50.0% by mass or less of the total mass of the liquid composition.
The water-soluble organic solvent may be the water-soluble organic
solvent that can be used in the ink described above. Water can be
deionized water (ion-exchanged water). The water content (% by
mass) of the liquid composition may be 50.0% by mass or more and
95.0% by mass or less of the total mass of the liquid composition.
The liquid composition may contain the additive agent(s) described
above for the ink. In particular, in one embodiment of the present
invention, the pH of the liquid composition may be adjusted to 3.5
or more and 5.5 or less with a pH-adjusting agent. Examples of the
pH-adjusting agent include, but are not limited to, organic acids,
such as acetic acid and methanesulfonic acid, inorganic acids, such
as sulfuric acid and nitric acid, and bases, such as alkali metal
hydroxide.
EXAMPLES
[0087] The present invention will be further described in the
following examples and comparative examples. However, the present
invention is not limited to these examples. Unless otherwise
specified, "part" in the examples is based on mass. The following
are abbreviations. [0088] IPDI: isophorone diisocyanate [0089] MDI:
dicyclohexylmethane diisocyanate [0090] HDI: hexamethylene
diisocyanate [0091] PPG: poly(propylene glycol) [0092] PEG:
poly(ethylene glycol) [0093] P(12BG): poly(1,2-butylene glycol)
[0094] P(13BG): poly(1,3-butylene glycol) [0095] PTMG:
poly(tetramethylene glycol) [0096] PC: polycarbonate diol [0097]
PES: polyester polyol [0098] PCL: polycaprolactone polyol [0099]
DMPA: dimethylolpropionic acid [0100] DMBA: dimethylolbutanoic acid
[0101] TMP: trimethylolpropane [0102] Gly: glycerin [0103] PE:
pentaerythritol [0104] PPT: polyoxypropylenetriol (Actcol 32-160,
manufactured by Takeda Pharmaceutical Co., Ltd.) [0105] EDA:
ethylenediamine
Preparation of Polyurethane Polymer Dispersion
Preparation of Polyurethane Polymer Dispersions PU-1 to PU-40
[0106] A polyisocyanate (A part and B part), a polyol (C part), a
diol having an acid group (D part), and methyl ethyl ketone (300
parts) in a four-neck flask equipped with a thermometer, an
agitator, a nitrogen inlet, and a reflux condenser were allowed to
react in a nitrogen gas atmosphere at 80 degrees Celsius for six
hours. A cross-linker (E part) was added to the flask and was
allowed to react at 80 degrees Celsius until a desired molar ratio
of the urethane bond to the urea bond was obtained while the
percentage of the unreacted isocyanate group was measured with an
FT-IR. The molar ratio of the urethane bond to the urea bond was
controlled by the method described above in detail. After
completing the reaction and cooling to 40 degrees Celsius,
ion-exchanged water was added to the flask, and aqueous potassium
hydroxide was added to the flask while stirring with a homomixer at
a high speed. The polymer solution was heated under reduced
pressure to evaporate methyl ethyl ketone, yielding polyurethane
polymer dispersions PU-1 to PU-40 each having a solid content of
20% by mass and a weight-average molecular weight of 35,000 or
more. Table 1 shows the preparation conditions for the polyurethane
polymer dispersions. The acid value, the molar ratio of the
urethane bond to the urea bond, and the gel fraction of each of the
polyurethane polymers were measured by the method described above.
Table 2 shows the properties of the polyurethane polymer
dispersions.
Preparation of Polyurethane Polymer Dispersion PU-45
[0107] IPDI (49.5 parts), PPG (number-average molecular weight:
2,000) (103.7 parts), DMPA (28.7 parts), and methyl ethyl ketone
(300 parts) in a four-neck flask equipped with a thermometer, an
agitator, a nitrogen inlet, and a reflux condenser were allowed to
react in a nitrogen gas atmosphere at 80 degrees Celsius for 7
hours. The percentage of the unreacted isocyanate group was zero as
measured with an FT-IR. HDI (14.3 parts) was added to the flask and
was allowed to react at 80 degrees Celsius. A cross-linker TMP (3.8
parts) was added to the flask and was allowed to react at 80
degrees Celsius until the molar ratio of the urethane bond to the
urea bond reached 95.0/5.0 while the percentage of the unreacted
isocyanate group was measured with an FT-IR. After completing the
reaction and cooling to 40 degrees Celsius, ion-exchanged water was
added to the flask, and aqueous potassium hydroxide was added to
the flask while stirring with a homomixer at a high speed. The
polymer solution was heated under reduced pressure to evaporate
methyl ethyl ketone, yielding a polyurethane polymer dispersion
PU-45 having a solid content of 20% by mass and a weight-average
molecular weight of 50,000. The acid value, the molar ratio of the
urethane bond to the urea bond, and the gel fraction of the
polyurethane polymer were measured by the method described above.
Table 2 shows the properties of the polyurethane polymer dispersion
PU-45.
TABLE-US-00001 TABLE 1 Preparation conditions for polyurethane (PU)
polymer dispersions PU Diol having acid polymer Polyisocyanate
Polyol group Cross-linker dispersion A B Number-average C D E No.
Type (parts) Type (parts) Type molecular weight (parts) Type
(parts) Type (parts) PU-1 IPDI 32.0 HDI 24.2 PPG 2000 111.2 DMPA
28.7 TMP 3.8 PU-2 MDI 37.5 HDI 24.0 PPG 2000 106.0 DMPA 28.7 TMP
3.8 PU-3 IPDI 31.9 HDI 24.1 PPG 2000 108.5 DMBA 31.7 TMP 3.8 PU-4
IPDI 32.9 HDI 24.9 PPG 2000 110.0 DMPA 28.7 Gly 3.8 PU-5 IPDI 31.5
HDI 23.9 PPG 2000 112.1 DMPA 28.7 PE 3.8 PU-6 IPDI 31.5 HDI 23.9
PPG 2000 112.1 DMPA 28.7 PPT 3.8 PU-7 IPDI 32.0 HDI 24.2 PPG 2000
111.2 DMPA 28.7 TMP/Gly 2.2/1.6 PU-8 IPDI 32.0 HDI 24.2 PEG 2000
111.2 DMPA 28.7 TMP 3.8 PU-9 IPDI 32.0 HDI 24.2 P(12BG) 2000 111.2
DMPA 28.7 TMP 3.8 PU-10 IPDI 32.0 HDI 24.2 P(13BG) 2000 111.2 DMPA
28.7 TMP 3.8 PU-11 IPDI 32.0 HDI 24.2 PTMG 2000 111.2 DMPA 28.7 TMP
3.8 PU-12 IPDI 32.0 HDI 24.2 PPG 2000 111.2 DMPA 28.7 TMP 3.8 PU-13
IPDI 32.0 HDI 24.2 PPG 2000 111.2 DMPA 28.7 TMP 3.8 PU-14 IPDI 32.0
HDI 24.2 PPG 2000 111.2 DMPA 28.7 TMP 3.8 PU-15 IPDI 32.0 HDI 24.2
PPG 2000 111.2 DMPA 28.7 TMP 3.8 PU-16 IPDI 32.0 HDI 24.2 PPG 2000
111.2 DMPA 28.7 TMP 3.8 PU-17 IPDI 31.6 HDI 23.9 PPG 2000 112.8
DMPA 28.7 TMP 3.0 PU-18 IPDI 32.9 HDI 24.9 PPG 2000 108.0 DMPA 28.7
TMP 5.7 PU-19 IPDI 30.3 HDI 22.9 PPG 2000 118.1 DMPA 28.7 -- --
PU-20 IPDI 61.4 HDI 5.2 PPG 2000 100.9 DMPA 28.7 TMP 3.8 PU-21 IPDI
7.0 HDI 47.4 PPG 2000 113.1 DMPA 28.7 TMP 3.8 PU-22 IPDI 57.7 HDI
4.3 PPG 2000 105.5 DMPA 28.7 TMP 3.8 PU-23 IPDI 5.8 HDI 44.6 PPG
2000 117.1 DMPA 28.7 TMP 3.8 PU-24 IPDI 68.1 -- 0 PPG 2000 99.4
DMPA 28.7 TMP 3.8 PU-25 IPDI 25.3 HDI 19.2 PPG 2000 132.6 DMPA 19.1
TMP 3.8 PU-26 IPDI 27.0 HDI 20.4 PPG 2000 127.3 DMPA 21.5 TMP 3.8
PU-27 IPDI 45.5 HDI 34.4 PPG 2000 68.5 DMPA 47.8 TMP 3.8 PU-28 IPDI
59.0 HDI 44.6 PPG 2000 25.7 DMPA 66.9 TMP 3.8 PU-29 IPDI 46.9 HDI
35.5 PPG 450 85.2 DMPA 28.7 TMP 3.8 PU-30 IPDI 29.1 HDI 22.0 PPG
4000 116.4 DMPA 28.7 TMP 3.8 PU-31 IPDI 32.0 HDI 24.2 PPG 2000
111.2 DMPA 28.7 TMP 3.8 PU-32 IPDI 23.6 HDI 17.9 PPG 2000 137.9
DMPA 16.7 TMP 3.8 PU-33 IPDI 60.6 HDI 45.9 PPG 2000 20.4 DMPA 69.3
TMP 3.8 PU-34 IPDI 48.6 HDI 36.8 PPG 400 82.1 DMPA 28.7 TMP 3.8
PU-35 IPDI 28.1 HDI 21.2 PPG 6000 118.2 DMPA 28.7 TMP 3.8 PU-36
IPDI 68.1 -- 0 PPG 2000 99.4 DMPA 28.7 TMP 3.8 PU-37 IPDI 32.0 HDI
24.2 PC 2000 111.2 DMPA 28.7 TMP 3.8 PU-38 IPDI 32.0 HDI 24.2 PES
2000 111.2 DMPA 28.7 TMP 3.8 PU-39 IPDI 32.0 HDI 24.2 PCL 2000
111.2 DMPA 28.7 TMP 3.8 PU-40 IPDI 70.6 -- -- PPG 2000 100.8 DMPA
28.6 TMP/EDA 4.0/3.2
TABLE-US-00002 TABLE 2 Characteristics of polyurethane (PU) polymer
dispersions Acid value (mgKOH/g) Percentage constituted by PU Acid
value of PU unit(s) derived from HDI with polymer Acid value
polymer resulting from Urethane respect to all units derived Gel
dispersion of PU unit(s) derived from bond/urea bond from
polyisocyanate in PU fraction No. polymer diol having acid group
(molar ratio) polymer (mol %) (%) PU-1 60 60 95.0/5.0 50 94 PU-2 60
60 95.0/5.0 50 94 PU-3 60 60 95.0/5.0 50 94 PU-4 60 60 95.0/5.0 50
94 PU-5 60 60 95.0/5.0 50 94 PU-6 60 60 95.0/5.0 50 94 PU-7 60 60
95.0/5.0 50 94 PU-8 60 60 95.0/5.0 50 94 PU-9 60 60 95.0/5.0 50 94
PU-10 60 60 95.0/5.0 50 94 PU-11 60 60 95.0/5.0 50 94 PU-12 60 60
85.0/15.0 50 94 PU-13 60 60 90.0/10.0 50 94 PU-14 60 60 98.5/1.5 50
94 PU-15 60 60 98.6/1.4 50 94 PU-16 60 60 100.0/0 50 94 PU-17 60 60
95.0/5.0 50 88 PU-18 60 60 95.0/5.0 50 100 PU-19 60 60 95.0/5.0 50
81 PU-20 60 60 95.0/5.0 10 94 PU-21 60 60 95.0/5.0 90 94 PU-22 60
60 95.0/5.0 9 94 PU-23 60 60 95.0/5.0 91 94 PU-24 60 60 95.0/5.0 0
94 PU-25 40 40 95.0/5.0 50 94 PU-26 45 45 95.0/5.0 50 94 PU-27 100
100 95.0/5.0 50 94 PU-28 140 140 95.0/5.0 50 94 PU-29 60 60
95.0/5.0 50 94 PU-30 60 60 95.0/5.0 50 94 PU-31 60 60 84.0/16.0 50
94 PU-32 35 35 95.0/5.0 50 94 PU-33 145 145 95.0/5.0 50 94 PU-34 60
60 95.0/5.0 50 94 PU-35 60 60 95.0/5.0 50 94 PU-36 60 60 100.0/0 0
94 PU-37 60 60 95.0/5.0 50 94 PU-38 60 60 95.0/5.0 50 94 PU-39 60
60 95.0/5.0 50 94 PU-40 60 60 84.0/16.0 0 94 PU-45 60 60 95.0/5.0
50 94
Preparation of Pigment Dispersion
Preparation of Pigment Dispersion A
[0108] A commercially available Cab-O-Jet 400 (manufactured by
Cabot Corp.) was well stirred in water to yield a pigment
dispersion A. Cab-O-Jet 400 is a self-dispersing carbon black
pigment having a hydrophilic group on the surface thereof. The
pigment dispersion A had a pigment content (solid content) of 15.0%
by mass and a pH of 9.0. The pigment had an average particle size
of 130 nm.
Preparation of Pigment Dispersion B
[0109] 1.5 g of 4-amino-1,2-benzenedicarboxylic acid was added to a
solution containing 5 g of concentrated hydrochloric acid dissolved
in 5.5 g of water at five degrees Celsius. A vessel containing this
solution was placed in an ice bath to maintain the solution at 10
degrees Celsius or less. 1.8 g of sodium nitrite dissolved in 9 g
of water at five degrees Celsius was added to the solution. After
the solution was stirred for 15 minutes, 6 g of carbon black was
added while stirring. The carbon black had a specific surface area
of 220 m.sup.2/g and a DBP absorption of 105 mL/100 g. After the
solution was stirred for another 15 minutes, the resulting slurry
was filtered through a filter paper (trade name standard filter
paper No. 2, manufactured by Advantec Toyo Kaisha, Ltd.). Particles
on the filter were sufficiently washed with water. The particles
were dried in an oven at 110 degrees Celsius to prepare
self-dispersing carbon black. The self-dispersing carbon black was
dispersed in water at a pigment content of 10.0% by mass to prepare
a dispersion. This pigment dispersion contained self-dispersing
carbon black having a --C.sub.6H.sub.3--(COONa).sub.2 group on the
surface thereof. Sodium ions of the pigment dispersion were then
substituted with potassium ions by an ion exchange method to
prepare a pigment dispersion B. The pigment dispersion B contained
carbon black having a --C.sub.6H.sub.3--(COOK).sub.2 group on the
surface thereof. The pigment dispersion B had a pigment content
(solid content) of 10.0% by mass and a pH of 8.0. The pigment had
an average particle size of 80 nm.
Preparation of Pigment Dispersion C
[0110] 500 g of carbon black having a specific surface area of 220
m.sup.2/g and a DBP absorption of 112 mL/100 g, 45 g of
aminophenyl(2-sulfoethyl)sulfone, and 900 g of distilled water in a
reactor were stirred at 300 rpm at a temperature of 55 degrees
Celsius for 20 minutes. 40 g of 25% by mass sodium nitrite was then
added dropwise to the mixture for 15 minutes. After 50 g of
distilled water was further added to the mixture, the mixture was
allowed to react at 60 degrees Celsius for two hours. The resulting
product was removed from the reactor while being diluted with
distilled water such that the solid content was 15.0% by mass.
After centrifugation and purification to remove impurities, a
dispersion (1) was obtained. Carbon black in the dispersion (1) had
aminophenyl(2-sulfoethyl)sulfone functional groups bonded to the
surface thereof. The number of moles of functional groups bonded to
carbon black in the dispersion (1) was determined as described
below. The sodium ion of the dispersion (1) measured with a
probe-type sodium electrode was converted into a value per mole of
carbon black powder to determine the number of moles of functional
groups bonded to carbon black. The dispersion (1) was then added
dropwise to a pentaethylenehexamine solution for one hour with
vigorous stirring while the temperature was maintained at room
temperature. The pentaethylenehexamine content ranged from 1 to 10
times the number of moles of sodium ions measured above. The amount
of solution was equal to the amount of dispersion (1). After this
mixture was stirred for 18 to 48 hours, the mixture was purified to
yield a dispersion (2) having a solid content of 10.0% by mass.
Carbon black in the dispersion (2) had pentaethylenehexamine bonded
to the surface thereof.
[0111] 190 g of a styrene-acrylic acid copolymer was weighed. The
styrene-acrylic acid polymer had a weight-average molecular weight
of 8,000, an acid value of 140 mgKOH/g, and a polydispersity Mw/Mn
of 1.5 (wherein Mw denotes the weight-average molecular weight, and
Mn denotes the number-average molecular weight). 1,800 g of
distilled water and potassium hydroxide for neutralizing the
polymer were added to dissolve the styrene-acrylic acid copolymer
while stirring, yielding an aqueous styrene-acrylic acid copolymer
solution. 500 g of the dispersion (2) was then added dropwise to
the aqueous styrene-acrylic acid copolymer solution while stirring.
This mixture of the dispersion (2) and the aqueous styrene-acrylic
acid copolymer solution was transferred to an evaporating dish, was
dried at 150 degrees Celsius for 15 hours, and was cooled to room
temperature. The dried product was then dispersed in distilled
water, which was adjusted to pH 9.0 with potassium hydroxide in
advance, with a dispersing apparatus. 1.0 N aqueous potassium
hydroxide was added to the dispersion while stirring to adjust the
pH within the range of 10 to 11. The dispersion was then desalted
and purified to remove impurities and coarse particles. Through
these procedures, a pigment dispersion C containing
polymer-attached carbon black dispersed in water was prepared. The
pigment dispersion C had a pigment content (solid content) of 10.0%
by mass and a pH of 10.1. The pigment had an average particle size
of 130 nm.
Preparation of Pigment Dispersion D
[0112] A styrene-acrylic acid copolymer having an acid value of 200
mgKOH/g and a weight-average molecular weight of 10,000 was
neutralized with 10% by mass aqueous potassium hydroxide. 10 parts
of carbon black having a specific surface area of 210 m.sup.2/g and
a DBP absorption of 74 mL/100 g, 20 parts of the neutralized
styrene-acrylic acid copolymer (solid content), and 70 parts of
water were mixed. This mixture was dispersed with a sand grinder
for one hour, was centrifuged to remove coarse particles, and was
filtrated under pressure through a microfilter having a pore size
of 3.0 micrometers (manufactured by FUJIFILM Co.). Through these
procedures, a pigment dispersion D in which carbon black was
dispersed in water by the polymer was prepared. The pigment
dispersion D had a pigment content (solid content) of 10.0% by mass
and a pH of 10.0. The pigment had an average particle size of 120
nm.
Preparation of Pigment Dispersion E
[0113] A pigment dispersion E in which carbon black was dispersed
in water by a polyurethane polymer was prepared in the same manner
as in the pigment dispersion D except that the styrene-acrylic acid
copolymer was replaced by the polyurethane polymer dispersion PU-1.
The pigment dispersion E had a pigment content (solid content) of
10.0% by mass and a pH of 10.0. The pigment had an average particle
size of 120 nm.
Preparation of Ink
[0114] A combination of the pigment dispersion, the polyurethane
polymer dispersion, and a salt shown in Tables 3 and 4 was mixed
with the following components. The amount of ion-exchanged water
(the remainder) was such that the total amount of the components of
the ink was 100.0% by mass. [0115] Pigment dispersion see Tables 3
and 4 [0116] Polyurethane polymer dispersion (polymer content
(solid content) was 20.0% by mass) see Tables 3 and 4 [0117] Salt
see Tables 3 and 4 [0118] Glycerin 9.0% by mass [0119] Diethylene
glycol 5.0% by mass [0120] Triethylene glycol 5.0% by mass [0121]
Acetylenol (trade name) E100 (surfactant, manufactured by Kawaken
Fine Chemicals Co., Ltd.) 0.1% by mass [0122] Ion-exchanged water
the remainder
[0123] The mixture was well dispersed and was passed through a
microfilter (manufactured by Fujifilm Corp.) having a pore size of
3.0 micrometers under pressure to prepare an ink.
TABLE-US-00003 TABLE 3 Preparation conditions for inks Pigment PU
polymer dispersion dispersion PU polymer Salt Example Content
Content content/pigment Content No. No. (mass %) No. (mass %)
content (times) Type (mass %) Example 1 A 20.00 PU-1 7.50 0.50 -- 0
Example 2 B 30.00 PU-1 7.50 0.50 -- 0 Example 3 C 30.00 PU-1 7.50
0.50 -- 0 Example 4 A 20.00 PU-2 7.50 0.50 -- 0 Example 5 A 20.00
PU-3 7.50 0.50 -- 0 Example 6 A 20.00 PU-4 7.50 0.50 -- 0 Example 7
A 20.00 PU-5 7.50 0.50 -- 0 Example 8 A 20.00 PU-6 7.50 0.50 -- 0
Example 9 A 20.00 PU-7 7.50 0.50 -- 0 Example 10 A 20.00 PU-8 7.50
0.50 -- 0 Example 11 A 20.00 PU-9 7.50 0.50 -- 0 Example 12 A 20.00
PU-10 7.50 0.50 -- 0 Example 13 A 20.00 PU-11 7.50 0.50 -- 0
Example 14 A 20.00 PU-12 7.50 0.50 -- 0 Example 15 A 20.00 PU-13
7.50 0.50 -- 0 Example 16 A 20.00 PU-14 7.50 0.50 -- 0 Example 17 A
20.00 PU-15 7.50 0.50 -- 0 Example 18 A 20.00 PU-16 7.50 0.50 -- 0
Example 19 A 20.00 PU-17 7.50 0.50 -- 0 Example 20 A 20.00 PU-18
7.50 0.50 -- 0 Example 21 A 20.00 PU-19 7.50 0.50 -- 0 Example 22 A
20.00 PU-20 7.50 0.50 -- 0 Example 23 A 20.00 PU-21 7.50 0.50 -- 0
Example 24 A 20.00 PU-22 7.50 0.50 -- 0 Example 25 A 20.00 PU-23
7.50 0.50 -- 0 Example 26 A 20.00 PU-24 7.50 0.50 -- 0 Example 27 A
20.00 PU-25 7.50 0.50 -- 0 Example 28 A 20.00 PU-26 7.50 0.50 --
0
TABLE-US-00004 TABLE 4 Preparation conditions for inks Pigment PU
polymer dispersion dispersion PU polymer Salt Content Content
content/pigment Content Example No. No. (mass %) No. (mass %)
content (times) Type (mass %) Example 29 A 20.00 PU-27 7.50 0.50 --
0 Example 30 A 20.00 PU-28 7.50 0.50 -- 0 Example 31 A 20.00 PU-29
7.50 0.50 -- 0 Example 32 A 20.00 PU-30 7.50 0.50 -- 0 Example 33 A
20.00 PU-1 7.50 0.50 Potassium phthalate 0.20 Example 34 A 20.00
PU-1 7.50 0.50 Potassium benzoate 0.20 Example 35 A 20.00 PU-1 7.50
0.50 Potassium sulfate 0.20 Example 36 A 20.00 PU-1 7.50 0.50
Potassium citrate 0.20 Example 37 A 20.00 PU-1 0.75 0.05 -- 0
Example 38 A 20.00 PU-1 30.00 2.00 -- 0 Example 39 A 20.00 PU-1
0.60 0.04 -- 0 Example 40 A 20.00 PU-1 30.75 2.05 -- 0 Example 41 A
20.00 PU-45 7.50 0.50 -- 0 Comparative example 1 A 20.00 PU-31 7.50
0.50 -- 0 Comparative example 2 A 20.00 PU-32 7.50 0.50 -- 0
Comparative example 3 A 20.00 PU-33 7.50 0.50 -- 0 Comparative
example 4 A 20.00 PU-34 7.50 0.50 -- 0 Comparative example 5 A
20.00 PU-35 7.50 0.50 -- 0 Comparative example 6 D 30.00 PU-36 7.50
0.50 -- 0 Comparative example 7 A 20.00 PU-37 7.50 0.50 -- 0
Comparative example 8 A 20.00 PU-38 7.50 0.50 -- 0 Comparative
example 9 A 20.00 PU-39 7.50 0.50 -- 0 Comparative example 10 D
20.00 PU-11 7.50 0.50 -- 0 Comparative example 11 E 30.00 PU-1 7.50
0.50 -- 0 Comparative example 12 A 20.00 -- 0 0 -- 0 Comparative
example 13 A 20.00 -- 0 0 Potassium phthalate 0.20 Reference
example 1 D 30.00 PU-1 15.00 1.00 -- 0 Reference example 2 D 30.00
PU-24 15.00 1.00 -- 0 Reference example 3 A 20.00 PU-40 7.50 0.50
-- 0
[0124] Polyurethane polymers and inks according to Comparative
Examples 14 to 20 were prepared as described below.
Comparative Example 14
[0125] An ink according to Comparative Example 14 was prepared as
described below with reference to Example 1 of PTL 4 (Japanese
Patent Laid-Open No. 2004-285344). 35 parts of poly(tetramethylene
ether) glycol, 3 parts of triethylene glycol, 16 parts of
dimethylolpropionic acid, 9 parts of tetramethylenexylylene
diisocyanate, and 25 parts of isophorone diisocyanate were allowed
to react in acetone in a nitrogen stream to yield a urethane
prepolymer. The urethane prepolymer was added dropwise and
dispersed in deionized water containing 12 parts of triethylamine.
The acetone was removed under vacuum to yield a polyurethane
polymer dispersion PU-41. PU-41 had a solid content of 30% by mass,
a weight-average molecular weight of 20,840, and an acid value of
69 mgKOH/g. 10.4 parts of a 25% by mass aqueous solution of a
potassium salt of a styrene-acrylic acid copolymer Joncryl 683
(manufactured by Johnson Polymer; acid value 160 mgKOH/g,
weight-average molecular weight 8,000), 71.5 parts of ion-exchanged
water, 5 parts of glycerin, 0.1 parts of Proxel GXL(S)
(manufactured by Avecia Ltd.), and 13 parts of carbon black MCF 88
(manufactured by Mitsubishi Chemical Corp.) were dispersed in a
bead mill with 0.8-mm zirconia beads such that the average diameter
of dispersed particles became 61.9 nm. After centrifugation, coarse
particles were removed by a 5-micrometer filter to yield a carbon
black dispersion. The carbon black dispersion was mixed with 26
parts of PU-41. 32.5 parts of triethylene glycol monobutyl ether,
32.5 parts of glycerin, 3.25 parts of Surfynol 465 (manufactured by
Air Products and Chemicals, Inc.), and 130.75 parts of
ion-exchanged water were added to the mixture to yield an ink
according to Comparative Example 14.
Comparative Example 15
[0126] An ink according to Comparative Example 15 was prepared as
described below with reference to Example 1 of PTL 2 (Japanese
Patent Laid-Open No. 2008-179657). A four-neck flask equipped with
a thermometer, an agitator, a nitrogen inlet, and a condenser tube
was charged with 95 g of Placcel 205BA (manufactured by Daicel
Chemical Industries, Ltd.), 11 g of trimethylolpropane, 120 g of
methyl ethyl ketone, and 0.54 g of 1,4-diazabicyclo[2.2.2]octane.
Placcel 205BA is a carboxylic-acid-modified polycaprolactone diol,
in which dimethylolbutanoic acid is modified with a lactone. After
agitation for 30 minutes, 74 g of isophorone diisocyanate was added
to the four-neck flask. After agitation at room temperature in a
nitrogen atmosphere for one hour, a reaction was performed at 70
degrees Celsius for four hours. After the reaction, the product was
cooled to room temperature to yield a 60% by mass urethane
prepolymer solution. 17.1 g of 50% by mass aqueous potassium
hydroxide and 350 g of ion-exchanged water were added to 250 g of
the urethane prepolymer solution in the four-neck flask and were
stirred at room temperature for 30 minutes. The mixture was heated
to 80 degrees Celsius in a nitrogen atmosphere and was subjected to
a chain extension reaction for two hours. After the reaction,
methyl ethyl ketone and part of water were removed with a rotatory
evaporator and an aspirator. Ion-exchanged water was then added
such that the amount of recovery was 429 g to yield a 35% by mass
polyurethane polymer dispersion PU-42. PU-42 had an acid value of
70 mgKOH/g and a weight-average molecular weight of 47,000.
[0127] After 3 kg of carbon black MA-100 (manufactured by
Mitsubishi Chemical Corp.) was mixed with 10 kg of water, the
mixture was added to 4.5 kg of a sodium hypochlorite solution
(available chlorine concentration 12%). After agitation at a
temperature in the range of 100 to 105 degrees Celsius for 10
hours, the resulting product was filtered. Dried wet crystals were
washed with water and were dried at 80 degrees Celsius to yield 2.5
kg of oxidized carbon black. The oxidized carbon black was mixed
with ion-exchanged water to prepare a slurry. The slurry was
dialyzed with a poly(methyl methacrylate) dialysis module Filtryzer
B3-20A (manufactured by Toray Industries, Inc.) to remove sodium
ions and chloride ions in the oxidized carbon black and was dried
to yield dialyzed oxidized carbon black. 120 g of the dialyzed
oxidized carbon black, 180 g of triethylene glycol monobutyl ether,
and 700 g of ion-exchanged water were mixed in a Homo Disper
agitator to prepare a slurry. A beaker containing the slurry was
connected to a circulation-type bead mill DYNO-Mill KDL-A
(manufactured by Willy A. Bachofen AG) through a tube. The slurry
was dispersed with zirconia beads having a diameter of 0.3 mm at
1,600 rpm for three hours to prepare an aqueous black pigment
dispersion. 0.7 g of 50% by mass aqueous potassium hydroxide, 0.5 g
of ion-exchanged water, and 7.1 g of the polyurethane polymer
dispersion PU-42 (solid content 35% by mass) were then added to
41.7 g of the aqueous black pigment dispersion to prepare an
aqueous black pigment dispersion (pigment content: 10% by mass,
polyurethane polymer content: 5% by mass). 25.8 g of ion-exchanged
water, 3.5 g of glycerin, 1.7 g of 2-pyrrolidone, and 1.5 g of
ethylene glycol were then added to 17.5 g of the aqueous black
pigment dispersion to prepare an ink according to Comparative
Example 15.
Comparative Example 16
[0128] An ink according to Comparative Example 16 was prepared as
described below with reference to Example 1 of PTL 1 (PCT Japanese
Translation Patent Publication No. 2005-515289). 6.5 parts of
self-dispersing carbon black that was manufactured in accordance
with International Publication WO 01/94476 and was surface-treated
by ozone oxidation, 0.1 parts of a polyurethane dispersion Hybridur
580 (manufactured by Air Products and Chemicals, Inc.), 1.5 parts
of a polyurethane dispersion Mace 85-302-1 (manufactured by Mace
Adhesives And Coatings Company Inc.), 9.5 parts of glycerin, 6
parts of ethylene glycol, 0.8 parts of Surfynol 465 (manufactured
by Air Products and Chemicals, Inc.), and 75.6 parts of water were
mixed to prepare an ink according to Comparative Example 16.
Comparative Example 17
[0129] An ink according to Comparative Example 17 was prepared as
described below with reference to Comparative Example 3 of PTL 3
(Japanese Patent Laid-Open No. 9-291242). 184.9 parts of
poly(tetramethylene glycol) (molecular weight 3,000, hydroxyl value
38 mgKOH/g), 15.1 parts of poly(ethylene glycol) (molecular weight
2,000, hydroxyl value 56 mgKOH/g), 21.5 parts of
2,2-dimethylolpropionic acid, and 200.0 parts of methyl ethyl
ketone in a reactor equipped with a thermometer, an agitator, a
reflux condenser tube, and a nitrogen gas-inlet pipe were heated to
50 degrees Celsius in a nitrogen atmosphere while stirring. After
the addition of 71.6 parts of isophorone diisocyanate, the mixture
was allowed to react at 80 degrees Celsius for 2.5 hours to yield
an isocyanate-group-containing prepolymer solution. After cooling
to 30 degrees Celsius, a solution of 6.9 parts of propylene glycol
and 229 parts of methyl ethyl ketone was added dropwise and was
allowed to react at 70 degrees Celsius. A liquid mixture of 9.8
parts of 28% by mass aqueous ammonia and 900 parts of water was
then added dropwise. The removal of the solvent yielded a
polyurethane polymer dispersion PU-43 having no urea bond. PU-43
had an acid value of 30 mgKOH/g, a pH of 8.5, and a solid content
of 25.0% by mass.
[0130] 250.0 parts of an ethylene-acrylic acid copolymer Primacor
5983 (manufactured by Dow Chemical Japan Ltd., acid value 156
mgKOH/g, melt index 500 g/10 minutes) were neutralized with 278.6
parts of 10% by mass aqueous sodium hydroxide and 471.4 parts of
ion-exchanged water and were then dissolved by heating to prepare
an aqueous ethylene-acrylic acid copolymer solution having a solid
content of 25% by mass and a pH of 9.0. 40.3 parts of the aqueous
ethylene-acrylic acid copolymer solution and 17.3 parts of the
polyurethane polymer dispersion PU-43 were mixed to prepare a
polymer composition. 15.0 parts of a phthalocyanine blue pigment
Lionol Blue FG-7350 (manufactured by Toyo Ink Co., Ltd.), 0.3 parts
of a silicone antifoaming agent, 2.0 parts of a polyethylene wax
dispersion (solid content 40% by mass), 4.5 parts of ethanol, and
20.6 parts of ion-exchanged water were then added to 57.6 parts of
the polymer composition to prepare an ink according to Comparative
Example 17.
Comparative Example 18
[0131] An ink according to Comparative Example 18 was prepared as
described below with reference to Example 3 of Japanese Patent
Laid-Open No. 2003-342502. 250 g of a commercially available carbon
black MA8 (manufactured by Mitsubishi Chemical Corp.) was well
dispersed in 1,000 ml of ion-exchanged water. 1,000 g of ammonium
peroxodisulfate was added to the dispersion and was stirred at a
temperature in the range of 60 to 70 degrees Celsius for eight
hours. The slurry was desalted with an ultrafiltration membrane
(manufactured by Toyo Roshi Kaisha, Ltd.) having a molecular weight
cut-off of 10,000 such that the electrical conductivity of the
filtrate was 0.5 ms/cm or less. The slurry was concentrated to a
solid content of 20% by mass. 20 g of 25% by mass aqueous potassium
hydroxide was added dropwise to adjust the pH of the slurry to 8.
Thus, a self-dispersing carbon black dispersion CB-1 having a solid
content of 15% by mass was prepared. The carbon black of CB-1 had
an average particle size of 85 nm, a polydispersity index of 0.15,
and a zeta potential of -50 mV.
[0132] A self-dispersing carbon black dispersion CB-1, an
acrylamide polymer Sumirez Resin 7200A (manufactured by Sumika
Chemtex Co., Ltd.), and a polyurethane polymer Superflex 150
(manufactured by Dai-ichi Kogyo Seiyaku Co., Ltd.) were mixed for
10 minutes at a mass ratio of 5.0:0.1:0.1 based on the solid
content. 20% by mass of diethylene glycol and 0.10% by mass of
Acetylenol (trade name) EH were then added to the mixture. Water
was then added to the mixture such that the carbon black content
(solid content) of the resulting ink was 5% by mass. The ink was
agitated for one hour. The ink was ultrafiltered through a
3-micrometer membrane filter (manufactured by Toyo Roshi Kaisha,
Ltd.) to prepare an ink according to Comparative Example 18.
Comparative Example 19
[0133] An ink according to Comparative Example 19 was prepared as
described below with reference to Example 4 of Japanese Patent
Laid-Open No. 2003-342502. An ink according to Comparative Example
19 was prepared in the same manner as in Comparative Example 18
except that the acrylamide polymer Sumirez Resin 7200A was replaced
by Polysol Cogum 15H (manufactured by Showa Highpolymer Co., Ltd.)
and the polyurethane polymer Superflex 150 was replaced by a
polyurethane polymer Superflex 300.
Comparative Example 20
[0134] An ink according to Comparative Example 20 was prepared as
described below with reference to Example 1 of Japanese Patent
Laid-Open No. 2008-280363. 202 parts of a castor-oil-modified diol
(manufactured by Hokoku Corp., number-average molecular weight
732), 32 parts of a castor-oil-modified diol (manufactured by
Hokoku Corp., number-average molecular weight 431), 79 parts of
dimethylolpropionic acid, 43 parts of polyoxyethylene ether glycol
PEG#600 (manufactured by NOF Corp.), 13 parts of propylene glycol,
76 parts of 1,6-hexamethylene diisocyanate, 155 parts of
hydrogenated MDI (dicyclohexylmethane diisocyanate), and 400 parts
of methyl ethyl ketone in a reactor equipped with an agitator, a
reflux condenser tube, a nitrogen inlet, and a thermometer were
heated to 75 degrees Celsius. After one hour, 0.3 parts of
dibutyltin laurate was added to the mixture. The mixture was kept
at 75 degrees Celsius so that the isocyanate group was decreased to
0.1% by mole or less. The reaction product was then cooled to 45
degrees Celsius or less. 40 parts of 25% by mass aqueous ammonia
and 1,400 parts of pure water were added while stirring for phase
inversion. Methyl ethyl ketone was removed under vacuum while
stirring at a temperature in the range of 20 to 60 degrees Celsius
to yield a polyurethane polymer dispersion PU-44 having a solid
content of 33% by mass and a pH of 6.7. 500 parts of a
self-dispersing carbon black dispersion Aqua-Black 174
(manufactured by Tokai Carbon Co., Ltd., solid content 20% by mass)
was added to 3 parts of the polyurethane polymer dispersion PU-44
and was stirred at room temperature for two hours to prepare an ink
according to Comparative Example 20.
Evaluation 1
[0135] In the following evaluation, the criteria AAA to B refer to
acceptable levels, and the criteria C and D refer to unacceptable
levels. The evaluation was performed with an ink jet recording
apparatus PIXUS iP3100 (manufactured by CANON KABUSHIKI KAISHA).
The recording conditions included a temperature of 23 degrees
Celsius, a relative humidity of 55%, and an ink droplet weight of
28 ng (within plus or minus 10%). With the ink jet recording
apparatus, an image that was recorded under the conditions under
which approximately 28 ng of one ink droplet was applied to a unit
area of 1/600 inches* 1/600 inches at a resolution of 600 dpi*600
dpi was assumed to have a print duty of 100%.
Optical Density 1
[0136] An ink cartridge filled with the ink prepared as described
above was placed in the ink jet recording apparatus. A 2 cm.times.2
cm solid image (print duty 100%) was printed on four recording
media: a PPC sheet GF-500 (manufactured by CANON KABUSHIKI KAISHA),
a PPC sheet 4024 (manufactured by Xerox Co.), a PPC sheet Bright
White (manufactured by Hewlett-Packard Co.), and a PPC sheet
Hammermill Jet Print (manufactured by International Paper). After
the solid image was left to stand for one day, the optical density
was measured with a reflection densitometer Macbeth RD-918
(manufactured by Macbeth). The following are evaluation criteria
for optical density. Tables 5 and 6 show the results.
[0137] AA: The average optical density of the four recording media
was 1.40 or more, and the highest optical density was 1.60 or
more.
[0138] A: The average optical density of the four recording media
was 1.40 or more, but the highest optical density was 1.55 or more
and less than 1.60.
[0139] B: The average optical density of the four recording media
was 1.40 or more, but the highest optical density was less than
1.55.
[0140] C: The average optical density of the four recording media
was less than 1.40.
Scratch Resistance of Image 1
[0141] An ink cartridge filled with the ink prepared as described
above was placed in the ink jet recording apparatus. A 1.0 inch*0.5
inches solid image (print duty 100%) was recorded on a PPC sheet
GF-500 (manufactured by CANON KABUSHIKI KAISHA). Ten minutes and
one day after the recording, a Silbon paper and a weight having a
contact pressure of 40 g/cm.sup.2 were placed on the solid image,
and the solid image and the Silbon paper were rubbed together.
After the Silbon paper and the weight were removed, smudges on the
solid image and a transfer to the white ground of the Silbon paper
were visually inspected. The following are evaluation criteria for
the scratch resistance of an image. Tables 5 and 6 show the
results. [0142] AAA: No smudge on the white ground was observed in
the test after 10 minutes and the test after one day. [0143] AA:
Little smudge on the white ground was observed in the test after 10
minutes, and no smudge on the white ground was observed in the test
after one day. [0144] A: Little smudge on the white ground was
observed in the test after 10 minutes and the test after one day.
[0145] B: Although unnoticeable smudges on the white ground were
observed in the test after 10 minutes, little smudge on the white
ground was observed in the test after one day. [0146] C: Smudges on
the white ground were observed in the test after 10 minutes and the
test after one day. [0147] D: Noticeable smudges on the white
ground were observed in the test after 10 minutes and the test
after one day.
Highlighter Resistance of Image 1
[0148] An ink cartridge filled with the ink prepared as described
above was placed in the ink jet recording apparatus. A vertical
rule having a width of 1/10 inches was recorded on a PPC sheet
GF-500 (manufactured by CANON KABUSHIKI KAISHA). Five minutes and
one day after the recording, the vertical rule was traced with a
yellow highlighter OPTEX2 (manufactured by ZEBRA Co., Ltd.), and
immediately after that a line was drawn with the yellow highlighter
on a white ground of a recording medium to check for contamination
of the pen nib and contamination of the line on the white ground.
The following are evaluation criteria for the highlighter
resistance of an image. Tables 5 and 6 show the results.
[0149] AAA: No contamination of the pen nib and no contamination of
the line on the white ground were observed in the test after five
minutes and the test after one day.
[0150] AA: In the test after five minutes, although coloring on the
pen nib was observed, little contamination of the line on the white
ground was observed. In the test after one day, there were no
contamination of the pen nib and no contamination of the line on
the white ground.
[0151] A: In the test after five minutes and the test after one
day, although coloring on the pen nib was observed, little
contamination of the line on the white ground was observed.
[0152] B: In the test after five minutes, although coloring on the
pen nib was observed, the contamination of the line on the white
ground was unnoticeable. In the test after one day, although
coloring on the pen nib was observed, little contamination of the
line on the white ground was observed.
[0153] C: In the test after five minutes and the test after one
day, there were coloring of the pen nib and contamination of the
line on the white ground. [0154] D: In the test after five minutes
and the test after one day, there were significant coloring of the
pen nib and significant contamination of the line on the white
ground.
Ink Ejection Stability
[0155] An ink cartridge filled with the ink prepared as described
above was placed in the ink jet recording apparatus. A 19 cm*26 cm
solid image (print duty 100%) was recorded on ten GF-500 PPC sheets
(manufactured by CANON KABUSHIKI KAISHA). The solid image on the
tenth sheet was visually inspected to evaluate ink ejection
stability. The following are evaluation criteria for ink ejection
stability. Tables 5 and 6 show the results.
[0156] A: Neither white streak nor faint streak was observed, and
the solid image was properly recorded.
[0157] B: A few unnoticeable white streaks or faint streaks were
observed.
[0158] C: Ink ejection was unstable, and white streaks or faint
streaks were observed on the image.
Prevention of Image Deflection
[0159] An ink cartridge filled with the ink prepared as described
above was placed in the ink jet recording apparatus. A 19 cm*26 cm
solid image (print duty 100%) was recorded on two GF-500 PPC sheets
(manufactured by CANON KABUSHIKI KAISHA). After the ink jet
recording apparatus was left to stand for 30 minutes, recording the
image on two GF-500 PPC sheets was performed ten times. A nozzle
check pattern was then recorded with the ink jet recording
apparatus (PIXUS iP3100). The nozzle check pattern was visually
inspected for image deflection. After the removal of a recording
head, the face of the recording head was observed with a microscope
to check for face wetting. The following are evaluation criteria
for image deflection and face wetting. Tables 5 and 6 show the
results.
[0160] AA: No disorder in the nozzle check pattern was observed,
indicating the prevention of image deflection. No face wetting was
observed.
[0161] A: No disorder in the nozzle check pattern was observed,
indicating the prevention of image deflection. Slight face wetting
was observed.
[0162] B: An unnoticeable disorder in the nozzle check pattern was
observed, indicating the prevention of image deflection. A little
face wetting was observed.
[0163] C: A significant disorder in the nozzle check pattern was
observed, and no satisfactory image was obtained, indicating the
occurrence of image deflection. Face wetting was also observed.
TABLE-US-00005 TABLE 5 Evaluation results Evaluation of image
Evaluation of ink Scratch Highlighter Prevention of Example No.
Optical density resistance resistance Ejection stability image
deflection Example 1 A AAA AAA A A Example 2 A AAA AAA A A Example
3 A AAA AAA A A Example 4 A AAA AAA A A Example 5 A AAA AAA A A
Example 6 A AAA AAA A A Example 7 A AAA AAA A A Example 8 A AAA AAA
A A Example 9 A AAA AAA A A Example 10 A B B A A Example 11 A AAA
AAA B A Example 12 A AAA AAA B A Example 13 A AAA AAA B A Example
14 A AAA AAA A B Example 15 A AAA AAA A A Example 16 A AAA AAA A A
Example 17 A B B A A Example 18 A B B A A Example 19 A AAA AAA A A
Example 20 A AAA AAA A A Example 21 A B B A A Example 22 A AAA AAA
A A Example 23 A AAA AAA A A Example 24 A B B A A Example 25 A B B
A A Example 26 A B B A A Example 27 A AAA AAA B A Example 28 A AAA
AAA A A Example 29 A AAA AAA A A Example 30 A B B A A Example 31 A
AAA AAA A A Example 32 A AAA AAA A A Example 33 AA AAA AAA A A
Example 34 AA AAA AAA A A Example 35 AA AAA AAA A A Example 36 AA
AAA AAA A A Example 37 A AAA AAA A A Example 38 A AAA AAA A A
Example 39 A B B A A Example 40 A AAA AAA B A Example 41 A AAA AAA
A A
TABLE-US-00006 TABLE 6 Evaluation results Evaluation of image
Evaluation of ink Optical Scratch Highlighter Ejection Prevention
of Example No density resistance resistance stability image
deflection Comparative example 1 A AAA AAA A C Comparative example
2 A AAA AAA C A Comparative example 3 A C C A A Comparative example
4 A C C A A Comparative example 5 A C C A A Comparative example 6 A
C C A A Comparative example 7 A C C C A Comparative example 8 A C C
C A Comparative example 9 A C C C A Comparative example 10 C AAA
AAA C A Comparative example 11 C B C C A Comparative example 12 A C
C A A Comparative example 13 AA D D A A Comparative example 14 C D
D B B Comparative example 15 A D D C A Comparative example 16 A C C
C A Comparative example 17 C D D C A Comparative example 18 B C C C
C Comparative example 19 B C C C C Comparative example 20 A C C C A
Reference example 1 C AAA AAA A A Reference example 2 C A A A AA
Reference example 3 B AAA AAA B C
[0164] Three minutes after the recording, the results of the
evaluation Scratch Resistance of Image and Highlighter Resistance
of Image for Example 41 were better than the results for Example
1.
Preparation of Ink 1 and 2
Ink 1
[0165] The pigment dispersion A and the polyurethane polymer
dispersion PU-1 were mixed with other components as described
below. [0166] Pigment dispersion A (pigment content (solid content)
was 10.0% by mass) 30.0% by mass [0167] Polyurethane polymer
dispersion PU-1 (polymer content (solid content) was 20.0% by mass)
7.5% by mass [0168] Glycerin 9.0% by mass [0169] Diethylene glycol
5.0% by mass [0170] Triethylene glycol 5.0% by mass [0171]
Acetylenol (trade name) E100 (surfactant, manufactured by Kawaken
Fine Chemicals Co., Ltd.) 1.0% by mass [0172] Ion-exchanged water
42.5% by mass
[0173] The mixture was well dispersed and was passed through a
microfilter (manufactured by Fujifilm Corp.) having a pore size of
3.0 micrometers under pressure to prepare an ink 1.
Ink 2
[0174] The pigment dispersion B and the polyurethane polymer
dispersion PU-1 were mixed with other components as described
below. [0175] Pigment dispersion B (pigment content (solid content)
was 10.0% by mass) 30.0% by mass [0176] Polyurethane polymer
dispersion PU-1 (polymer content (solid content) was 20.0% by mass)
7.5% by mass [0177] Glycerin 9.0% by mass [0178] Diethylene glycol
5.0% by mass [0179] Triethylene glycol 5.0% by mass [0180]
Acetylenol (trade name) E100 (surfactant, manufactured by Kawaken
Fine Chemicals Co., Ltd.) 1.0% by mass [0181] Ion-exchanged water
42.5% by mass
[0182] The mixture was well dispersed and was passed through a
microfilter (manufactured by Fujifilm Corp.) having a pore size of
3.0 micrometers under pressure to prepare an ink 2.
Preparation of Liquid Composition
Liquid Composition 1
[0183] The following components were mixed. The amount of
ion-exchanged water (the remainder) was such that the total amount
of the components of the ink was 100.0% by mass. [0184] Reactant:
calcium nitrate 5.0% by mass [0185] Glycerin 5.0% by mass [0186]
1,5-pentanediol 5.0% by mass [0187] Trimethylene glycol 7.0% by
mass [0188] Acetylenol (trade name) E100 (surfactant, manufactured
by Kawaken Fine Chemicals Co., Ltd.) 0.1% by mass [0189]
Ion-exchanged water the remainder
[0190] The mixture was well dispersed and was passed through a
microfilter (manufactured by Fujifilm Corp.) having a pore size of
3.0 micrometers under pressure to prepare a liquid composition
1.
Liquid Composition 2
[0191] A liquid composition 2 was prepared in the same manner as in
the liquid composition 1 except that the reactant calcium nitrate
was replaced by aluminum nitrate.
Liquid Composition 3
[0192] A liquid composition 3 was prepared in the same manner as in
the liquid composition 1 except that the reactant calcium nitrate
was replaced by yttrium nitrate.
Liquid Composition 4
[0193] A liquid composition 4 was prepared in the same manner as in
the liquid composition 1 except that the reactant calcium nitrate
was replaced by magnesium nitrate.
Liquid Composition 5
[0194] The following components were mixed. The amount of
ion-exchanged water (the remainder) was such that the total amount
of the components of the ink was 100.0% by mass. [0195] Reactant:
sodium citrate 10.0% by mass [0196] Glycerin 5.0% by mass [0197]
1,5-pentanediol 5.0% by mass [0198] Trimethylolpropane 7.0% by mass
[0199] NIKKOL BC-20 (surfactant, manufactured by Nikko Chemicals
Co., Ltd.) 1.0% by mass [0200] Ion-exchanged water the
remainder
[0201] The mixture was well dispersed and was passed through a
microfilter (manufactured by Fujifilm Corp.) having a pore size of
3.0 micrometers under pressure. The mixture was then treated with
sulfuric acid to prepare a liquid composition 5 having a pH of
4.0.
Liquid Composition 6
[0202] A liquid composition 6 was prepared in the same manner as in
the liquid composition 5 except that the pH was 3.0.
Liquid Composition 7
[0203] A liquid composition 7 was prepared in the same manner as in
the liquid composition 5 except that the pH was 3.5.
Liquid Composition 8
[0204] A liquid composition 8 was prepared in the same manner as in
the liquid composition 5 except that the pH was 5.5.
Liquid Composition 9
[0205] A liquid composition 9 was prepared in the same manner as in
the liquid composition 5 except that the pH was 6.0.
[0206] The absorbances of the liquid compositions 1 to 9 without
dilution were measured with a Hitachi double-beam spectrophotometer
U-2900 (manufactured by Hitachi High-Technologies Corp.). Any of
the liquid compositions had a ratio Amax/Amin of the maximum
absorbance Amax to the minimum absorbance Amin of 1.0 or more and
2.0 or less at a wavelength in the range of 400 to 780 nm.
Evaluation 2
[0207] In the following evaluation, the criteria AAA to B refer to
acceptable levels, and the criteria C and D refer to unacceptable
levels. The Optical Density, Scratch Resistance of Image, and
Highlighter Resistance of Image were evaluated with an ink jet
recording apparatus PIXUS Pro9500 (manufactured by CANON KABUSHIKI
KAISHA). The recording conditions included a temperature of 23
degrees Celsius and a relative humidity of 55%. An ink cartridge
separately filled with the ink and the liquid composition listed in
Table 7 was placed in the ink jet recording apparatus PIXUS
Pro9500. The ink was contained in a chamber for yellow, and the
liquid composition was contained in a chamber for gray. Recording
was performed unidirectionally from the home position to the
opposite position. The width of the recording corresponded to the
nozzle width of the head. After the liquid composition was applied,
the ink was applied on the liquid composition in the same pass to
form an image. With the ink jet recording apparatus, an image
recorded under the conditions under which approximately 16 ng of
one ink droplet was applied to a unit area (one pixel) of 1/600
inches* 1/600 inches at a resolution of 600 dpi*600 dpi was assumed
to have an ink print duty of 100%. An image recorded under the
conditions under which approximately 7 ng of one droplet of the
liquid composition was applied to one pixel was assumed to have a
liquid composition print duty of 100%.
Optical Density 2
[0208] An ink cartridge filled with the ink and the liquid
composition prepared as described above was placed in the ink jet
recording apparatus. A 2 cm*2 cm solid image (ink and liquid
composition print duties 100%) was printed on four types of
recording media: a PPC sheet GF-500 (manufactured by CANON
KABUSHIKI KAISHA), a PPC sheet 4024 (manufactured by Xerox Corp.),
a PPC sheet Bright White (manufactured by Hewlett-Packard Co.), and
a PPC sheet Hammermill Jet Print (manufactured by International
Paper). After the solid image was left to stand for one day, the
optical density was measured with a reflection densitometer Macbeth
RD-918 (manufactured by Macbeth). The following are evaluation
criteria for optical density. Table 7 shows the results.
[0209] AA: The average optical density of the four recording media
was 1.40 or more, and the highest optical density was 1.60 or
more.
[0210] A: The average optical density of the four recording media
was 1.40 or more, but the highest optical density was 1.55 or more
and less than 1.60. [0211] B: The average optical density of the
four recording media was 1.40 or more, but the highest optical
density was less than 1.55. [0212] C: The average optical density
of the four recording media was less than 1.40.
Scratch Resistance of Image 2
[0213] An ink cartridge filled with the ink and the liquid
composition prepared as described above was placed in the ink jet
recording apparatus. A 1.0 inch*0.5 inches solid image (ink and
liquid composition print duties 100%) was recorded on a PPC sheet
GF-500 (manufactured by CANON KABUSHIKI KAISHA).
(1) Evaluation of Scratch Resistance of Image Three Minutes After
Recording
[0214] Three minutes after the recording, a Silbon paper and a
weight having a contact pressure of 40 g/cm.sup.2 were placed on
the solid image, and the solid image and the Silbon paper were
rubbed together. After the Silbon paper and the weight were
removed, smudges on the solid image and a transfer to the white
ground of the Silbon paper were visually inspected. The following
are evaluation criteria for the scratch resistance of an image.
Table 7 shows the results.
[0215] AA: No smudge on the white ground was observed in the test
after three minutes.
[0216] A: Little smudge on the white ground was observed in the
test after three minutes.
[0217] B: Unnoticeable smudges on the white ground were observed in
the test after three minutes.
[0218] C: Smudges on the white ground were observed in the test
after three minutes.
[0219] D: Noticeable smudges on the white ground were observed in
the test after three minutes.
(2) Evaluation of Scratch Resistance of Image 10 Minutes and One
Day After Recording
[0220] Ten minutes and one day after the recording, a Silbon paper
and a weight having a contact pressure of 40 g/cm.sup.2 were placed
on the solid image, and the solid image and the Silbon paper were
rubbed together. After the Silbon paper and the weight were
removed, smudges on the solid image and a transfer to the white
ground of the Silbon paper were visually inspected. The following
are evaluation criteria for the scratch resistance of an image.
Table 7 shows the results.
[0221] AAA: No smudge on the white ground was observed in the test
after 10 minutes and the test after one day.
[0222] AA: Little smudge on the white ground was observed in the
test after 10 minutes, and no smudge on the white ground was
observed in the test after one day.
[0223] A: Little smudge on the white ground was observed in the
test after 10 minutes and the test after one day. [0224] B:
Although unnoticeable smudges on the white ground were observed in
the test after 10 minutes, little smudge on the white ground was
observed in the test after one day. [0225] C: Smudges on the white
ground were observed in the test after 10 minutes and the test
after one day. [0226] D: Noticeable smudges on the white ground
were observed in the test after 10 minutes and the test after one
day.
Highlighter Resistance of Image 2
[0227] An ink cartridge filled with the ink and the liquid
composition prepared as described above was placed in the ink jet
recording apparatus. A vertical rule having a width of 1/10 inches
was recorded on a PPC sheet GF-500 (manufactured by CANON KABUSHIKI
KAISHA).
(1) Evaluation of Highlighter Resistance of Image Three Minutes
After Recording
[0228] Three minutes after the recording, the vertical rule was
traced with a yellow highlighter OPTEX2 (manufactured by ZEBRA Co.,
Ltd.), and immediately after that a line was drawn with the yellow
highlighter on a white ground of a recording medium to check for
contamination of the pen nib and contamination of the line on the
white ground. The following are evaluation criteria for the
highlighter resistance of an image. Table 7 shows the results.
[0229] AA: No contamination of the pen nib and no contamination of
the line on the white ground were observed in the test after three
minutes.
[0230] A: In the test after three minutes, although coloring on the
pen nib was observed, little contamination of the line on the white
ground was observed.
[0231] B: In the test after three minutes, although coloring on the
pen nib was observed, the contamination of the line on the white
ground was unnoticeable.
[0232] C: In the test after three minutes, there were coloring of
the pen nib and contamination of the line on the white ground.
[0233] D: In the test after three minutes, there were significant
coloring of the pen nib and significant contamination of the line
on the white ground.
(2) Evaluation of Highlighter Resistance of Image Five Minutes and
One Day After Recording
[0234] Five minutes and one day after the recording, the vertical
rule was traced with a yellow highlighter OPTEX2 (manufactured by
ZEBRA Co., Ltd.), and immediately after that a line was drawn with
the yellow highlighter on a white ground of a recording medium to
check for contamination of the pen nib and contamination of the
line on the white ground. The following are evaluation criteria for
the highlighter resistance of an image. Table 7 shows the results.
[0235] AAA: No contamination of the pen nib and no contamination of
the line on the white ground were observed in the test after five
minutes and the test after one day. [0236] AA: In the test after
five minutes, although coloring on the pen nib was observed, little
contamination of the line on the white ground was observed. In the
test after one day, there were no contamination of the pen nib and
no contamination of the line on the white ground. [0237] A: In the
test after five minutes and the test after one day, although
coloring on the pen nib was observed, little contamination of the
line on the white ground was observed. [0238] B: In the test after
five minutes, although coloring on the pen nib was observed, the
contamination of the line on the white ground was unnoticeable. In
the test after one day, although coloring on the pen nib was
observed, little contamination of the line on the white ground was
observed. [0239] C: In the test after five minutes and the test
after one day, there were coloring of the pen nib and contamination
of the line on the white ground. [0240] D: In the test after five
minutes and the test after one day, there were significant coloring
of the pen nib and significant contamination of the line on the
white ground.
TABLE-US-00007 [0240] TABLE 7 Combination of liquid composition and
ink and evaluation results Evaluation of image Scratch resistance
Highlighter resistance (1) 3 min (2) 10 min and (1) 3 min (2) 5 min
and Liquid composition Ink Optical after 1 day after after 1 day
after Example No. No. density recording recording recording
recording Example 42 Liquid composition 1 Ink 1 AA AAA AA AAA AA
Example 43 Liquid composition 1 Ink 2 AA AAA AA AAA AA Example 44
Liquid composition 2 Ink 1 AA AAA AA AAA AA Example 45 Liquid
composition 3 Ink 1 AA AAA AA AAA AA Example 46 Liquid composition
4 Ink 1 AA AAA A AAA A Example 47 Liquid composition 5 Ink 1 AA AAA
AA AAA AA Example 48 Liquid composition 6 Ink 1 AA AAA AA AAA AA
Example 49 Liquid composition 7 Ink 1 AA AAA AA AAA AA Example 50
Liquid composition 8 Ink 1 AA AAA AA AAA AA Example 51 Liquid
composition 9 Ink 1 AA AAA B AAA B
[0241] When the liquid composition had a pH of less than 3.5, as in
Example 48, the wettability of a member in contact with the liquid
composition was inferior to the liquid composition having a pH of
3.5 or more (for example, Example 49).
[0242] While the present invention has been described with
reference to exemplary embodiments, it is to be understood that the
invention is not limited to the disclosed exemplary embodiments.
The scope of the following claims is to be accorded the broadest
interpretation so as to encompass all such modifications and
equivalent structures and functions.
[0243] This application claims the benefit of Japanese Patent
Application No. 2011-075884, filed Mar. 30, 2011 and Japanese
Patent Application No. 2011-075885, filed Mar. 30, 2011, which are
hereby incorporated by reference herein in their entirety.
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